Chapter - 1 INTRODUCTION TO DATABASES

Transcription

1 Chapter - 1 INTRODUCTION TO DATABASES A database is an integrated collection of inter-related data, stored with minimum redundancy and serves many users/application quickly and efficiency. A database system is basically a computerized record keeping system, i.e. it is a computerized system whose overall purpose is to maintain information and to make the information available on demand. DBMS is a collection of integrated data and set of programs that allow several users to access and manipulate the data. Its main purpose is to provide users with an abstract view of the data i.e. the system hides certain details of how the data is stored and maintained. Application programs Database End Users End User 1 Programmer 1 Table 1 Table 2 End User 2 Programmer 2 Table 3 Table 4 Programmer 3 End User 3 Database: Database management is divided into four main components. They are: It consists of collection of persistent data that is used by the application system. Hardware: The processors and associated main memory that are used to support the execution of the database system software. Software: The layer between the physical database and the users that handles all request from the users for access to the database. 1

2 Users: There are of three types of users: Application Programmers: End User: Users who are responsible for writing application programs that use the database. The users that interact with the system to access the database from online workstation using the interface (SQL) provided with the system. DataBase Administrator (DBA): DBA is the person who makes strategies and policy decision regarding the data. He provides the technical support for implementing those decisions. Thus the DBA is responsible for the overall control of the system Database Management System Database management systems have evolved from hierarchical to network to relational models. The widely acceptable database model is the relational model. The relational database management system uses only its relational capabilities to manage the information stored in the database. The relational model has three major aspects: Structure : There are well-defined objects that store the database. Structure and the data contained within them can be manipulated by operations. Operation: There are clearly defined actions that allow users to manipulate the data and structures of a database. The operation on a database must adhere to a pre-defined set of integrity rules. Integrity rules: They are the laws that govern which operations are allowed on the data and structures of a database. Integrity rules protect the data and structure of a database. Types of DBMS There are four major categories of DBMS data models:- Hierarchical: e.g. IMS System 2000 Network: e.g. IDMS Total Inverted List: e.g.adabas Model 204 Datacom 2

3 Relational: e.g. DB2, SQL/DS, Ingress, Oracle Comparison of DBMS and RDBMS DBMS The relation between two files has to be maintained programmatically if required. Client/server architecture is not normally Supported. RDBMS Relationship can be specified while creating structures itself. Most RDBMS support Client/Server architecture. Distributed database is not supported. Supports Distributed database. Least security: anyone can access records DBMS Multiple level of security maintained Login Security Command Level Security Object Level security RDBMS Follows less than six Codd s Rules Follows most of the Codd s rules (above 10) Advantages of RDBMS 1. Redundancy can be reduced: In non-database systems, each application or department has its own private files resulting in considerable amount of redundancy of stored data. Thus space is wasted. By having a centralized database, redundancy and other related issues can be controlled. 2. Data independence: In conventional file based application, programs need to know the data organization and access technique to be able to access the data. So changes in the data organization will necessitate changes in the application program. In RDBMS, the application programs are transparent to the physical organization and access techniques. 3

4 In addition, enhancement of the database to hold more information does not affect application programs, which do not need that enhanced information. 3. Ensure access and integrity: Integrity of data refers to the correctness, consistency and inter-relationship of the data with respect to the application, which uses the data. There are many aspects to integrity and RDBMS covers most of these. To name a few often there is a need to ensure that certain field values are not duplicated across records. Such restrictions, known as primary key constraints can be defined to the DBMS. Though facilities for defining primary keys are available in the file system, the application program must know the use of the index, adheres in RDBMS the use of the primary key need not be reflected in the application programs. Database 4. Referential Integrity Rules: Data integrity rules, which define the relationship between different files, are called referential integrity rules. They are provided for by RDBMS to a varying degree, as against file system, which do not provide any referential integrity. 5. Sharing data: DBMS allows many applications to share the data. This helps new application to use existing database. If the database is managed in a controlled manner, new application can be added with marginal modifications/ additions to the database. 6. Recovery from failure: Multiple updates to the database can be clubbed together as a single logical transaction. The RDBMS will ensure that updates physically take place only when the logical transaction is complete. The database therefore, will never be in a state where only some of the updates of the logical transaction have taken place. 7. Uniform security and privacy through password, view and automatic backup: RDBMS provide tools by which the DBA can ensure security of the data lying in the database. The access to the database is typically through user codes and passwords allocated by the DBA. The DBA can restrict the type of the data available to a user and also type of operation that can be done be user. 4

5 A database is a collection of data. A database can be viewed as an organized mechanism that has the capability of storing information, through which a user can retrieve the stored information in an effective and efficient manner. Relational Database A relational database is a database divided into logical units called tables, where tables are related to one another within the database. A relational database allows data to be broken down into logical, smaller more manageable units allowing for easier maintenance and providing more optimal database performance according to the level of organization. Tables are related in a relational database, allowing adequate data to be retrieved in a single query. By having common keys or fields among relational database tables, data from multiple tables can be joined to form one large result set. Relational database is a database composed of related objects, primarily tables. A table is the most basic means of storage for data in a database. Characteristic Of A Relational DBMS Model The relational data management model eliminated all parent-child relationships and instead represented all data in the database as simple row/column tables of data values. A relation is similar to table with rows/columns of data values. The rows of a table are referred to as Tuples and the columns are referred to as Attributes. Several tuples of equal length placed one below the other create table. Each table is an independent entity and there is no physical relationship between tables. Most table data management system based on the relational model have a built-in support for query languages like ANSI SQL or QBE (Query By Example). These queries are simple English construct that allows adhoc data manipulation from a table. Relational model of data management is based on set theory. Built-in query language is designed in the RDBMS, so that it can manipulate sets of data (one or more tuples). The user interface used with relational models is non-procedural because only what needs to be done is specified and not how it has to be done. Using any of the other methods, you have not only to specify what needs to be done but how it has to be done as well. An RDBMS software should obey Codd s twelve rules for it to be relational. The twelve E.F Ted Codd s laws: Relational Database Management A relational database management system uses only its relational capabilities to manage the information stored in its database. 5

6 Information Representation All information stored in a relational database is represented only by data item values, which are stored in the tables that make up the database. Associations between data items are not logically represented in any other way, such as, by the use of pointers from one table to the other. Logical Accessibility Every data item value stored in a relational database is accessible by stating the name of the table it is stored in, the name of the column under which it is stored and the value of the primary key that defines the row in which it is stored. Representation of null values The database management system has a consistent method for representing null values. For example null values for numeric data must be distinct from zero or any other numeric value and for character data it must be different from a string of blanks or any other character value. Catalog facilities The logical description of a relational database is represented in the same manner as ordinary data. This is done so that the facilities of the relational database management system itself can be used to maintain database description. Data Language A relational database management system may support many types of language for describing data and database. However there must be at least one language that uses ordinary character string to support the definition of data, the definition of views to manipulation of data, constraints on data integrity, information concerning authorization and the boundaries for recovery of units. View Updatability Any view that can be defined using combination of base tables, is capable of being applied to an insert, update or delete operation as well. Physical data independence Changes made to physical storage representation or access method do not require changes to be made to application program. 6

7 Logical data independence Changes made to tables that do not modify any data stored in that table, do not require changes to be made to application programs. Integrity Constraints Constraints that apply to entity integrity and referential integrity are specifiable by the data language implemented by the database management system and not by the statement coded into the application program. Database Distribution The data language implemented by the relational database management system supports the ability to distribute the database without requiring changes to be made to application programs. The facility must be provided in the data language whether or not the database management system itself supports distributed databases. Non Subversion If the relational database management system supports facilities that allow application programs to operate on the tables a row at a time an application program using this tupel of database access is prevented from bypassing entity integrity or referential integrity constraints that are defined for the database Data Modeling using ERD (Entity Relationship Diagrams) Entity-Relationship Diagrams Entity: Entity is an object that is distinct and is distinguishable from other objects. The distinction is accomplished by associating with each entity a set of attributes, which describe that object. e.g. An employee is an entity. An employee is distinct from another may be by using name, date of birth etc. Attribute: Attribute is a set of characteristics that is possessed by an entity, which helps in distinguishing an entity from another entity. e.g.: For the entity employee characteristics of name, date of birth, address are attributes. 7

8 An attribute which has an unique value for each occurrence of entity is referred to as an identifying attribute or identifier. Where two or more attributes are required to form an identifier, it is referred to as concatenated identifier. Relationship Relationship is an entity or a function that serves to interconnect to or more entitles. Types of relationships One to one (1:1 ) One element of an entity has relation to one and only one element of another entity. E.g.: one employee has one and only one pf_no One to many (1:N) An element of any entity may have relation to one element of another element. e.g. one employee can belong to only one department but one department can have more than one employee. Many to Many (N: N) Many elements of an entity are related to more than one element of another entity. e.g. one supplier can supply many products and similarly one products may be supplied by more than one supplier. Attribute: Attribute is a set of characteristics that is possessed by an entity, which helps in distinguishing an entity from another entity. e.g. For the entity employee characteristics that is possessed by an entity which helps in distinguishing an entity from another entity. e.g. For the entity employee characteristics of name, date of birth address are the attributes. An attribute which has an unique value for each occurrence of entity is referred to as an identifying attribute or identifier. Where two or more attributes are required to form an identifier it is referred to as a concatenated identifier. Normalizing the Data The data in an RDBMS must be organized into related tables, which is referred to as normalizing the data. Normalization is the process of organizing data into related tables. By 8

9 normalizing the data you are attempting to eliminate redundant data. There are rules established for the normalization of the data. These rules are known as: Normalization is a process of simplifying the relationship between the data in an n-tuple. It is carried out for the following reasons: Simplify the maintenance of data through update, insert and delete. Simple retrieval of data in response to queries and request. Avoid structuring data when new application requirements arise. Structure the data so that any relationship can be easily represented. First Normal From [FNF]- This rule states that a column cannot contain multiple values. For example a persons name can be broken down into last name, middle name and the first name to follow FNF. value. Example: A relation is in FNF if the interaction of any column and row contains only one Table: Customer Name Address Credit_status Jones Leeds Bad Jones Truro Bad Smith Bristal Good Smith Ely Good Brows Bath Good Brows Fife Good Customer table is said to be FNF. First it contains redundant information, for example: Smith s credit status good is repeated several times. This will lead to update difficulties when Smith s credit_status Good is repeated several times. This will be lead to update difficulties when Smith s credit_status changes. Secondly the Name attribute can longer serve as a unique identifying field, since the name value for it can occur many times in different rows of the table. Second Normal From [SNF] This rule states that every non-key column must depend on the entire key and not just a part of the primary key. Eg. If you are using a customer ID and part number for a key, all the columns in that table must apply only to a particular customer and part number together. So a part_description would not belong in this table. A table must also comply with first normal form to be in second normal form. Rule: 9

10 A table in FNF is also in SNF if the values in every column are directly or indirectly transitively dependent on the complete unique identifier (primary key). Table: ORDER_ITEM ORDER NO ITEM_NAME QUANTITY ITEM_PRICE 123 AXE HOE SPADE AXE HOE 5 10 ORDER_ITEM table lists the items contained within various orders, the quantity of each associated with the order and their unit prices. ORDER_NUMBER and ITEM_NAME attributes combined identifies row uniquely. This table is in FNF, because ITEM_PRICE is not directly dependent on the ORDER_NUMBER component of primary key, but only on the ITEM_PRICE is not directly dependent on the ORDER_NUMBER component of primary key, but only on the ITEM_NAME component. QUANTITY,on the other hand, is directly dependent on both components of the primary key. To put this information into SNF, the single table must be decomposed into tables as follows: TABLE : ORDERS ITEM_NAME ITEM_PRICE AXE 15 HOE 10 SPADE 13 Third Normal Form [TNF] - This rule much like the previous one and states that all non key columns must not depend on any other non key columns. E.G. If you have a table that has addresses in it, the zip code must not send on another non key field like state. It should depend on the entire primary key. Of course, the table must comply with second normal form. The TNF is often violated for convenience sake. Third Normal Form (TNF) Rule : A relation in SNF is also in TNF if the values in every non key column are not transitively dependent on the primary key. TABLE : BORROWING 10

11 BOOK_ID PERSON_ID DURATION LIBRARIAN_ID LIBARIAN_GRADE DBMS S days L001 ASST DFS S days L001 ASST AFM S days L001 ASST DBMS S days L002 IN-CHRG LOC S days L002 IN-CHRG The above table lists book borrowing from various local libraries with the duration of the borrowing, the library staff member who signed out the book and grade of that librarian. Concatenating the identification of the book and the identification of the borrower identifies borrowings. The table is in SNF< but not in TNF, because B is only indirectly dependent on the primary key (@BOOK PERSON-ID ). It is directly dependent on the identity of the LIBRARIAN_ID. To out this information into TNF the single table (BORROWING) must be decomposed into two tables as follows: TABLE: BORROWING Book_id PERSON_ID DURATION DBMS S days DFS S days AFM S days DBMS S days LOC S days TABLE :LIBRARIAN LIBRARIAN_ID L001 LOO2 LIBRARIAN_GRADE ASST IN_CHRG SQL Server uses a type of database called a Relational Database. Relational databases are database in which data is organized into tables. Tables are organized by grouping data about the same subject and contain columns and rows of information. A database can generally be thought of as a collection of related data. In earlier database products a database was usually just a file_something like employee.dbf, which contained a single table of data products a database was usually just a file-something like employee.dbf, which contained a single table of data. Inside the employee.dbf file were columns relating to employee data such as salary, hire date, name, Social Security number, and so on. There was a row for each person in the company, with corresponding values in the appropriate columns. Indexes, used to speed data access, were in a separate file, was any security file, as was any security- related item. In SQL Server, a database is not necessarily a file it is more of a logical concept based on a collection of related objects. For example, a database in SQL Server contains not only the raw 11

12 database, any indexes, the security of the database, and perhaps other such as views or related to that particular database. Relational Database Objects As you just saw, a relational database is compared of different types of objects. These objects are all described in more detail in the particular day s lesson that applies to them. The following are some of the more common objects: Tables: These are the objects that contain the data types and actual raw data. Columns: These are the parts of the table holding the data. Columns must be assigned a data type and unique name. Data types: There are various data types to choose from, such as character, numeric, or date. A single data type is assigned to a column within a table. Stored procedures: These are like macros in that Transact-SQL code can be written and stored under a name. By executing the stored procedure, you actually run the Transact- SQL code within the procedure. One use would be to take the Transact-SQL code that runs a weekly report, save it as a stored procedure, and from then on just run the stored procedure to generate the report. Stored procedure can also be used as security mechanisms. Triggers are stored procedures that activate when data is added, modified, or deleted from the database. They are used to ensure that business rules or other data integrity rules are enforced in the database. For example, a trigger can ensure that every book in a bookstore has a valid publisher assigned to it. Rules: Rules are assigned to columns that data being entered must conform to standards you set. For example, rules can be used to make sure that a person s phone number contains only numbers. Primary keys: Although not objects per se, keys are essential to relational databases. Primary keys enforce uniqueness among rows, providing a way to uniquely identify every item you want to store. Foreign keys: Again, not objects per se, foreign keys are columns that reference the primary keys or unique constraints of other tables. SQL Server uses primary and foreign keys to relate the data back together from separate tables when queries are performed. Constraint: Constraints are server-based, system-implemented data-integrity enforcement mechanisms. 12

13 Defaults: Defaults can be set on fields so that if no data is entered during an INSERT operation, default values will be used. An example is setting the area code for the area where most of your customers come from, which saves you from entering the area code for local customers. Views: Views are basically queries stored in the database that can reference one or many tables. You can create and save them so you can use them easily in the future. Views usually either exclude certain columns from a table or link two or more tables together. You can also use them as security mechanisms. Indexes: Indexes can help organize data so that queries run faster. 13

14 Exercise : 1. Fill in the blanks 1. is the layer between the physical database and the users that handles all requests from the users for access to the database. 2. rules govern which operations are allowed on the data and structures of a database. 3. The rows of a table are referred to as and the columns are referred to as. 4. is an object that is distinct and is distinguishable from other objects. 2. True or False 1. A database is an integrated collection of inter-related data, stored with minimum redundancy and serves many users/application quickly and efficiency. 2. Data integrity rules, which define the relationship between different files are called referential integrity. 3. The RDBMS update a record even though the logical transaction may not be complete 4. Attribute is a set of characteristic that is possessed by an entity which helps in distinguishing an entity from another entity. 5. Normalizing the data does not eliminate redundant data. 3. Answer the following: 1. What is a database and explain the four components of Database management system. 2. Distinguish between DBMS and RDBMS 3. Does RDBMS have an advantage over DBMS. Explain. 4. What is the significance of Codd s rules. 5. What is normalization and what are the stages of normalization? 6. List with a brief description the Relational database objects. 7. What is the difference between entity and attribute? 14

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16 Chapter - 2 GETTING STARTED WITH SQL-SERVER IBM invented a computer language back in the 1970s designed specially for database queries called SEQUEL, which stood for Structured English Query Language Overtime this language has been added to, so that is not a language just for queries but can also qbe used to build database and manage security of the database engine. IBM released SEQUEL into the public domain, where it become known as (pronounced as SEQUEL or spell it as S-Q-L ) Microsoft s SQL Server is a client/server database engine, so it is important for you to understand the client/server model. A client/server application can be defined as one that s is split into two parts: One part runs on a server and the other part runs on workstations. The server side of the application provides security, fault tolerance, performance, concurrency and reliable backups. The client side provides the user interface and contains empty reports, queries and forms. SQL Server is the part of the equation, various clients to choose from can connect to SQL Server, including the utilities that come with SQL Server, such as SQL Server Query Analyzer SQL Server provides the following advantages for both clients and servers. Client advantages Easy to use Supports multiple hardware platforms Supports multiple software applications Familiar to the user. Server Advantages Reliable Concurrent Sophisticated locking Fault tolerance High-performance hardware Centralized control In client/server computing, when a query is run, server searches the database and sends only the rows that are a match to the client. This not only saves the bandwidth, but it can be faster than having the workstation perform the query, as long as the server is a powerful enough machine. Editions of SQL Server: Microsoft has simultaneously released four editions of the SQL Server 7.0 Standard Edition 16

17 This version of the product supplies full functionality and is intended to run on a Windows NT Server 4.0 or later computer. Enterprise Edition The Enterprise Edition of SQL Server 7.0 is for every high-end installation. It runs on Window NT Server 4.0 Enterprise Edition (or later) and provides features such as large memory support (greater thanm 2 GB of RAM), Microsoft Clustering support (high availability support) and support for upto 32 CPUs. Small Business Server Edition The Small Business Server (sbs) edition of SQL Server 7.0 is a solution for small business (generally fewer than 50 users). It supports up to four processors and upto 2 GB of RAM, but it is limited to 50 users and a database cannot exceed 10GB in size. Desktop Edition The Desktop Edition runs on Windows 95 and Windows 98 (windows 9x) and Windows NT workstation 4.0 or later. It is meant as a development and remote SQL Server installation to support a central server. It can support several users simultaneously but is typically meant for fewer than 10 users. There s no limit on database size but Windows NT workstation supports only two processors and Window 9x supports one processor. SQL Server Hardware Requirements Supported Hardware The lowest-powered CPUs supported are Pentium 166 processors and DEC Alpha processors, Pentium, Pentium Pro, and Pentium 11 computers are also supported. At least 32 MB of RAM is required although the Enterprise Edition requires 64MB of RAM. The amount of disk space required varies, based on software components. A minimal install will require atleast 65 MB of space on your hard drive and a full install will require about 180MB of hard drive space. Any additional SQL Server components, such as Microsoft English Query will require more space. Starting SQL Server 7.0 To start SQL Server Click on programs Go to Microsoft SQL Server 7.0 A number of options would be available namely: Books online, client Network utility, Enterprise Manager, Import and export data, Query analyzer Server Manager etc. 17

18 We shall be focusing only on three major options: Service Manager Enterprise Manager Query Analyzer Service Manager The SQL Server Service Manager utility enables you to control the SQL Server-related service on your computer (or any SQL Server computer on your network). When you start this utility you see something similar. 18

19 The SQL Server service manager utility enables you to control the SQL server related services on your computer. The Server field contains the name of the server you are monitoring. The services box shows which service you are examining, and there is a graphical representation of the state of the service. When a service is running, the green light will show. This indicates that in this case, the MSSQLServer service is currently running. This is the main service that runs SQL server. The Server field contains the name of the server you are monitoring. The Services box shows which service you are examining, and there is a graphical representation of the state of the service. When a service is currently running, this is the service that runs SQL Server. You can also stop or pause a service. Some services do not support being paused, and those that do vary in their behavior. For example, the MSSQLServer service will continue to function when paused, but new connection will not be allowed. There is also an option to auto-start each service when the operating system starts. This option is especially handy on Windows 9x computer because they don t have services that can be configured to start automatically. Simply make sure the check box next to the Auto-Start Service When OS Starts is checked for each service you want to have started automatically. The Services drop-down list shows which services can be controlled from this utility. This includes the MSSQLServer service, the SQLServerAgent service, the MSDTC service, and (if 19

20 installed) the Microsoft Search service. You can use the server drop-down list to select another server. The list can be somewhat unreliable, and the utility is flexible enough to allow you to simply type the name of the server you d like to examine. After you ve typed a server name, click the dropdown list for services. The service manager will then attempt to connect to the remote server. The functionality of this application is also available from SQL Server Enterprise Manager. However the service Manager runs from your taskbar and is very convenient to access. SQL Server Default Login Ids The sa login is a member of the sysadmin role fixed by the server role. As a member of this role, sa can do anything in SQL Server. The sa account always exists and cannot be dropped. The password for sa is blank right after the installation which can be changed later. For now, the easiest way to do this is to click Start, programs, Microsoft SQL Server 7.0, Query Analyzer. Change the server name to your computer name, and check the box Start SQL Server if stopped. Select to use SQL Server authentication, enter a Login Name of sa, and leave the password blank. After you have completed the dialog, click OK. You will be logged in, and SQL Server will be started if it wasn t already running. The letters sa stand for system administrator. 20

21 Click on Microsoft SQL Server 7.0 Query Analyzer to open the Query Analyzer Query Analyzer The SQL Server Query Analyzer is your primary interface for running SQL statements, Transact-SQL queries or stored procedures. Using SQL Server Login and User Security, every operation in SQL Server is a secure operation. Therefore, you must first log in and identify yourself to any SQL Server to which you want to connect. As mentioned in the discussion of the Client Configuration utility you can enter (local) to connect to your local copy of SQL Server. You can also leave the server name blank. The Query Analyzer will figure out what you mean and connect to your SQL Server. Use a login name of sa and no password. On case-sensitive servers, the login is also case sensitive, so make sure you enter it in lowercase. After you ve clicked OK or pressed Enter, you will be logged into the appropriate instance of SQL Server. 21

22 After you have successfully logged in, you can start running Transact- SQL queries. The Query Analyzer tool provides a workspace to perform select, update, delete queries and database definition queries using SQL scripts. If you need to check the structure of a table or the data it contains, you can use Query Analyzer to quickly get the information you need. When selecting data, you can save the results as a tab-delimited file or as a comma-separated file. This can be a quick way to export data to another application or computer system. When writing scripts, you can test your scripts for syntax and for performance without actually executing the statement. This option is the Show Query Plan setting on the General tab of the Current Connection Options window available under the Query menu. This is useful when writing larger SQL scripts, so you can check your script while writing it. The Query Toolbar button. You can open multiple windows inside the Query Analyzer by selecting the New Query The file Open button will open the standard dialog box to find Transact-SQL scripts, which by default have a SQL extension. The Save Query/ buttons will either save the text in your query window to a file or if you have run a query and selected the results window, save the results of a query you have run. The next button with the X clears the query window of any text so you can start with a clean slate. 22

23 The next several buttons are the windows standard Cut, Copy, Paste and Find buttons, which are enabled when appropriate. The next button gives you the option of determining where your results will appear when you run the query. The default is to simply display whatever text is returned from SQL Server. The grid option works very nicely because many names in SQL Server can be 128 Unicode characters in length. The default of displaying the text will usually pad out all 128 characters will spaces if the names are not fully used. The Grid option typically leaves enough space only for the widest data column to be displayed. After you have typed in queries, you can verify whether they have been entered correctly clicking the blue checkmark on the toolbar. SQL Server will parse then query meaning it will check that s syntactically correct. To actually run the query, click the play button / select Query, Execute from the menu, type F5 on your keyboard. After the query is run, the results pane appears with all information. The Stop option on the toolbar is enabled when you run a query. You can cancel a query while it is still running. panel. GO back to the Text v/s Grid option. Run the following query and examine the results Running Queries: 23

24 If you look at the bottom of the screen, you will see s Grid # 1, s Grid #2 and Messages. The results of the first query are shown in s Grid#1, second in s Grid#2 and the messages on the Messages tab. The Advanced tab configures items such as how to align the results of your queries and maximum number of characters that can be returned for single column of data. The drop down box next to the DB label provides a list of the installed database on the server to which you are connected. If you change the value here, the SQL script will use that installed database unless you specify a different database in the SQL script itself. Configuration Under the File menu is the Configure window, where you can change the default file extensions for queries and results. The option can be handy for saving scripts for different purposes with different extensions. For example, you could save table creation scripts with a.ddl extension instead of the default.sql extension to help differentiate these types of scripts from data manipulation scripts. 24

25 Context-Sensitive Help Context-sensitive help for Transact-SQL is available in the query pane. Press Shift+F1 after selecting all or part of your SQL script to display the context-specific help on Transact-SQL syntax in the Help window. Color Coding and Fonts One of the first things you will notice in Query Analyzer is the color coding. For example, the default color coding is blue for keywords, green for comments, and red for strings. You can change the default color coding by accessing the Font window under the View menu item or by right-clicking the mouse on either pane of the Query Analyzer window. In the Font window, you can also change the fonts used in Query Analyzer. Notice that the color coding and font settings are specific to the pane currently selected. This means you can select different fonts for the query and the resultsets. The same font settings are also used when printing. s Pane When running your query, you have the option of displaying the resultset in the standard results pane or a grid results pane. One of the advantages of using the grid results pane, is that you can resize a column by dragging one of its edges. Graphical SQL Execution Plan Query Analyzer provides a graphical execution plan with details on each execution step that supply the optimizer s reasons and explanation for the query plan. Details include estimated row counts and estimated costs for the step. The explanation for the step describes how the particular operation works. The execution plan even gives warnings when statistics on tables are missing and should be updated. The Show Query Plan option provides similar, but less detailed, information in a text-only format. This option is available by using the Set Showplan_Text On statement. Clicking Display Estimated Execution Plan on the Query menu accesses the graphical execution plan. Index Analysis An analysis of your query for possible index performance improvements is available by choosing Query, Index Analysis from the menu or by pressing Ctrl+I. Query Analyzer displays the results of the index analysis. The analysis might be a suggested index scheme. If the analysis can t find an index scheme, then no indexes are recommended. Notice the list of reasons for not recommending many indexes. If Query Analyzer can determine that a new index will enhance your query s performance, a dialog box prompts you to accept the recommended index. After accepting the index, the query is created. This is an easy-to-use tool to get indexing recommendations for queries when you need them to run with the best performance possible. 25

26 When generating indexes, you should be aware of their performance downside, however. Indexes can lower performance of database inserts, deletes, and updates because both the index and the underlying data must be updated and maintained. CREATE DATABASE To create a database in SQL Server Enterprise Manager : Start the SQL Server Enterprise Manager by selecting the Start button, Programs, Microsoft SQL Server Enterprise Manager Connect to your SQL server Expand the Database folder The SQL Server Databases On installing SQL Server 7.0 the databases installed would be Master, Tempdb, MSDB, Pubs, and Northwind. Some of these (master, model, tempdb, and MSDB) are system databases. Do not drop any of these databases without important reason it may cause serious harm on SQL- Server. The other two, the pubs and Northwind databases, are simply samples to assists you in learning SQL Server. The Master Databases The Master databases is the key databases for running SQL Server. It contain a pointer to the primary data file for every databases installed on your system, as well as key server wide information. This server wide information includes such items as system wide error messages, login information, system stored procedures, and connected or linked servers. 26

27 The Model Databases The Model database is the best of as template database. Each time you create a new database, the model database is actually copied, and then the size and other changes you requested for your new database are applied. Therefore any object that exists in the model database will be copied to the new database as it is created. For example you can place a table or a username in this database right after you install SQL Server. Each time a database is created after that, the table and your username appear in every database. The model database is about 1.5MB after installation. Because the model is copied to create each new database, no database can be smaller than the model. The Tempdb Database The Tempdb database is where sorts, joins, and other activities that require temporary space are performed. It is approximately 2.5MB after installation, but as is the case with all database in SQL Server 7.0 by default, it can grow as you need more space. The Tempdb database is reinitialized each time SQL Server (the MSSQLServer service) is restarted. The MSDB Database The MSDB database supports the SQL Server Agent service, including storing information about jobs, alerts, events, and replication. A history of all backup and restore activity is also kept in this database. The MSDB database is about 8.5MB by default. The Pubs Database The pubs database is meant to be a learning tool. It contains a sample database about a publisher, including authors, books and sales. Most of the examples in the SQL Server Books Online are based on the pubs database. Most database features are highlighted via their implementation in the pubs database. Pubs is just under 2MB in size after installation. The Northwind Database The Northwind database is an alternative learning database to the pubs database. Northwind has been the sample database supplied with Microsoft Access for the some time now. Because more and more Microsoft Access users are migrating to SQL Server, the Northwind database was brought over to assist them in learning the features of the product with a familiar database. Northwind is about 4MB by default. Right -click on either the Database folder or in the white space in the right pane, and choose New Database from the context menu. Specify the database name. 27

28 If you look at the File properties at the bottom of the dialog, you will note that the automatically grow File option is turned on and that File Growth properties have been set. In addition to this, the maximum file size is set to Unrestricted Filegrowth. To change the properties of the database files, check the appropriate box and make the modifications. Click the transaction Log tab. It will have a default name and will be 1MB. Creating a database using the SQL Server Query Analyzer utility. CREATE DATABASE database_name [ON {(PRIMARY] (NAME = logical_name, FILENAME = physical_name [,SIZE = size] [,MAXSIZE = max_size : UNLIMITED] [,FILEGROWTH = growth_increment]) )[, n]] [LOG ON {(NAME = logical_name, 28

29 FILENAME = physical_name [,MAXSIZE = max_size : UNILIMTED] [,FILEGROWTH = growth_increment])} [, n]] [FOR LOAD : FOR ATTACH] As you can see from the preceding syntax, the items necessary to create a database are the database name, the logical name of the primary database file, the physical name of the database s primary file, and the transaction log s logical and physical filenames. The following list describes the different CREATE DATABASE parameters: database_name---this parameter refers to the database as a whole. ON PRIMARY---This parameter specifies to which filegroup this database file is a member. The default filegroup is Primary. NAME---This parameter specifies the logical name you will use within SQL Server to refer to the physical database file on the hard disk. FILENAME---This parameter is the pathname and filename pertaining to the data that will be stored on hard disk. SIZE---This parameter specifies how big the database file should be. This value can be expressed in either megabytes or kilobytes. The default size is the size of the Model file. To specify megabytes or kilobytes, attach the MB or KB suffix to your size parameter. For example, 10MB would create a 10 megabyte file. MAXSIZE--- This parameter specifies the maximum size to which the database can dynamically grow. If you do not specify a size here and the autogrowth option is turned on, your database could grow to fill entire hard disk. This parameter is also expressed in either megabytes or kilobytes. FILEGROWTH---This parameter specifies which increments are used for the auto growth of this database file. It can be expressed as either a number of megabytes, kilobytes, or as a percentage of the size of the time of the growth. The default, if not specified, is 1 MB. USE master GO CREATE DATABASE Frogger ON PRIMARY ( NAME = FroggerData, FILENAME = C:\MSSQL7\DATA\FroggerData.mdf, SIZE = 20MB, MAXSIZE = 100MB 29

30 Creating Tables Tables FILEGROWTH = 10MB ) LOG ON ( NAME = FroggerLog, FILENAME C:\MSSQL7\DATA\FroggerLog.1df, SIZE = 5MB, MAXSIZE = 15MB, FILEGROWTH = 1MB ) GO Tables store all the data in your database and are organized into rows and columns (records and fields). Each column in your table can store a specific type of information or data type. A single table represents an entity in your database. Each row in the table represents an occurrence of that entity. The column in your table describe the attributes of that logical entity. For example, you might create a table of employees (where employees are a logical entity). A single row in your employees table represents a single instance of an employee. The columns that make up table describe the employee. Some columns you might include are EmployeeID, FirstName, SSN (Social Security Number), and others. Columns Each column (field) in your table must be assigned a name, a data type, optionally a length, and a nullability status. You can place columns in any order in your table definition. Each column must also have a unique name within the table and follow the rules for SQL Server identifiers. A single database can have up to 2 billion tables in it, with each table holding up to 1,024 columns. The maximum length of any row is 8,092 bytes. Rules of the language Identifiers can be from 1 to 128 Unicode characters in length including letters, symbols, and numbers. The first character must be a letter or the following #, or and # have special meanings in SQL Server. You can use the following symbols after the first character: #, $, and_. Identifiers that begin with symbols are used as local variable. Note that symbol can appear only as the first character in an identifier. 30

31 Identifiers that begin with the # symbol are used to signify that the object you are creating is a temporary object and can be referenced by the user during the session. Identifiers that begin with the ## symbol are used to signify that the object you are creating is a temporary object and can be referenced by all user in the database. You can use embedded spaces in your identifiers, but to reference those objects you must encapsulate them in either double quotation marks or square brackets. For example, a table named Employee Pension would need to be referenced as Employee Pension or [Employee Pension in the database. It is preferable (if you insist on using spaces in your identifier names) to use the square brackets syntax so as not to confuse constant strings with SQL Server identifiers. Data Types The data type specifies what kind of information (numeric, character, and so on) and how much space that information takes up in a particular column. Some data types have a variable length, while others have a fixed length. SQL Server data type can be broken down into the following groups: string, binary, integer, approximate and exact numeric, special, date and time, money, autoincrementing, synonyms, user-defined, and computed column. The table lists the different data types allowed in SQL Server 7.0. SQL Server 7.0 Supported Data Types Category Data type Comments String char (n), varchar Stores character Strings. Binary binary (n), varbinary Stores binary information in two-byte pairs. Integer int, smallint, tinyint Stores integer values. Approx. Numeric float, real Stores exact numeric information Special bit, text, image Stores a single bit, character information greater than 8000 bytes or image data Date and Time date time, Small date time Stores dates and times. Money money, small money Stores currency values. Auto-incrementing time stamp Stores values that automatically incremented. Integers 31

32 Bit : Integer data with either a 1 or 0 value. Int : Integer (whole number) data from -2^31 (-2,147,483,648) through 2^31-1 (2,147,483,647). Smallint : Integer data from 2^15 (-32,768) through 2^15-1 (32,767). Tinyint : Integer data from 0 through 255. Decimal and Numeric Decimal : Fixed precision and scale numeric data from -10^38-1 through 10^38-1. Money and Smallmoney Money : Monetary data values from -2^63 (-922,337,203,685, ) through 2^63-1 (+922,337,203,685, ), with accuracy to a ten-thousandth of a monetary unit. Smallmoney : Monetary data values from -214, through +214, , with accuracy to a ten-thousandth of a monetary unit. Approximate Numerics Float : Floating precision number data from -1.79E through 1.79E Real : Floating precision number data from -3.40E + 38 through 3.40E Datetime Datetime : Date and time data from January 1, 1753, to December 31, 9999, with an accuracy of three-hundredths of a second, or 3.33 milliseconds. Smalldatetime : Date and time data from January 1, 1900, through June 6, 2079, with an accuracy of one minute. Character Strings Char : Fixed-length non-unicode character data with a maximum length of 8,000 characters. Varchar : Variable-length non-unicode data with a maximum of 8,000 characters. Text : Variable-length non-unicode data with a maximum length of 2^31-1 (2,147,483,647) characters. Image: Variable-length binary data with a maximum length of 2^31-1 (2,147,483,647) bytes. 32

33 Exercise : 1. Fill in the blanks a) A client/server application can be defined as one that is split that into two parts: One part runs on the and the other on. b) Microsoft released four editions of the SQL Server 7.0 edition :,, and. c) The SQL Server utility enables you to control the SQL Server related services on your computer. d) The Master database contains important information such as,,, or. e) The database is where sorts, joins and other activities that require temporary space are performed. f) is an integer data with either a 1 or 0 value. g) is a datatype used to store monetary data values. 2. What do you understand by client-server database engine. Is SQL Server a client-server database engine. 3. Mention the editions of SQLSever. Explain each. 4. Match the columns Datatype Varchar Binary Tiny int Real Small date time Money Description Stores dates and times Stores integer values Stores currency values Stores character strings Stores values that are automatically incremented Stores binary information in two-byte pairs. 33