DEVELOPING DATABASE APPLICATIONS (INTERMEDIATE MICROSOFT ACCESS, X405.5)

Transcription

1 Technology & Information Management Instructor: Michael Kremer, Ph.D. Database Program: Microsoft Access Series DEVELOPING DATABASE APPLICATIONS (INTERMEDIATE MICROSOFT ACCESS, X405.5) Section 1

2 WHO AM I? Michael Kremer Currently: Federal Reserve Bank Previously: Lawrence Berkeley Laboratory Database/Application Developer dbase, Access Developer for over 20 years Instructor for UC Extension since 1998 DB: Oracle, SQL Server, Access Prog.: ASP.net. C#, VB/VBA, Java/Javascript Reporting: Cognos, Actuate

3 WHO ARE YOU? Name/Company/Organization What do you do? Computer Experience (OS, Application SW, Other Classes Taken, etc.) MS Access Experience Expectations/Goals Any other information about you such as hobbies, special interests, fun facts, etc.

4 AGENDA 1. Introduction to Application Development 2. Exchanging Data using MS Access 3. Linking External Data 4. Importing External Data 5. Exporting MS Access Data 6. Linking MS Access Tables

5 Introduction to Application Development 1.

6 1.1 APPLICATION DEVELOPMENT STEPS 1 Database design is only one step within the Software Development Life Cycle (SDLC) process. System Analysis is a main step before database design Planning Phase. Clearly identify scope and goals. Planning phase sets boundaries for the application process. Make sure that everyone involved in the project agrees on the goals and the scopes of the project. System Analysis: Determine goal of the overall project (not only the system). Establish system design s criteria (yard stick) Define clearly scope

7 1.1 APPLICATION DEVELOPMENT STEPS 2 Next step is database design: Data collection Identifying data elements Data Normalization Conceptual model is independent of physical implementation Refine conceptual model and transform it into a logical model (particular data model such as relational, hierarchical, object-oriented). Then transform logical model into physical database. After building the database the user interface must be designed. Selecting application software, prototype forms/reports, navigational system. Finally application can be built in its entirety. User interface is the main bridge between technical community and diverse user community Very important.

8 1.1 APPLICATION DEVELOPMENT STEPS 3 Important aspects about user interfaces: Consistency Forgiveness Simplicity Aesthetics Feedback Testing is an important step before application is released. Review all aspects of the application with all parties involved. Refine the application, if necessary, and test again. Once testing is done, distribute the application (installing). Last two steps are mostly neglected due to time constraints: Documenting an application is as crucial as training the users on the new application. Documentation is important in the future to help support staff maintain and upgrade an application. Initial and possibly ongoing user training is critical to obtaining accurate data stored in the database.

9 1.2 LIFE CYCLE MODELS 4 Ideally, finish one step in SDLC before starting the next one. This model assumes that all the information necessary for each step is available. Furthermore, it assumes that the information remains constant over the lifetime of the project. Unfortunately, reality is different from this approach.

10 1.2 LIFE CYCLE MODELS 5 As we all know, all these different steps interact with each other. There is always a need to go back and make adjustments due to new information discovered or changed information. Due to shortcomings of Waterfall model other approaches have been developed. Spiral model tries to overcome the lack of flexibility with an iterative repetition of the steps in waterfall mode.

11 1.2 LIFE CYCLE MODELS 6 Entire scope is not considered until very late in the development phase. One should keep the entire scope of a project in mind at all times, from the very beginning though the end of the project. Both models lack certain aspects of the real-world project development, however, combining them into a new model may work. The beginning of a project can be modeled after the waterfall model, (system analysis, the design of database and user interface). After the initial phase, an approach closer to the spiral model should be taken to accomplish the remaining steps: Building the database Building the interface Testing the application Other models: Iterative and Incremental Development Agile Development Rapid Application Development

12 Exchanging Data using MS Access 2.

13 2.1 METHODS OF WORKING WITH EXTERNAL DATA 7 In today s information driven society, it is absolutely crucial to exchange data between different systems. MS Access is no exception, in fact, due to its versatility in exchanging data it has become a very popular desktop database product. Below are categories of applications Access can communicate with: Other Windows application Macintosh applications (Foxbase, FoxPro, Excel) Spreadsheets PC based database applications Server-based database applications Text Files HTML files Mail Servers/Clients Web Services

14 2.1 METHODS OF WORKING WITH EXTERNAL DATA 8 The following lists all native (built-in) file formats: Access databases(all versions) MS Excel (*.xls) Exchange (*.pst) Outlook (*.pst) Text files(*.txt, *.csv, *.tab, *.asc) HTML documents (*.html, *.htm) SharePoint lists XML files (*.xml) Access can export and import data in many different formats. Incoming data can be imported or linked: Linking Data: Data remains in its native format outside Access Importing Data: Data is copied and converted into Access

15 2.1 METHODS OF WORKING WITH EXTERNAL DATA Linking Data Linking to external data keeps the data in its current file format. There is no data duplication, and MS Access can make changes (with some exceptions) to the data, even to the non-native index files. This is useful when the other application is still in use. However, performance is degraded due to constant translation of data formats back and forth between MS Access and the external file format. Importing Data Importing the data makes a copy of the data, converts the data into a MS Access format, and creates tables in MS Access. More efficient in terms of performance, and useful if the other application is not in use anymore. But if the external application is still being used, maintaining data in two different places causes problems. Also consider that importing a lot of data increases the size of the MS Access database file. 9

16 2.1 METHODS OF WORKING WITH EXTERNAL DATA Linking vs. Importing You should consider importing external data when: Data is small and is not changed frequently by users of the native system. No need to share data you create with users of the other database application. Replacing the old database application and no need of the old formatted data. Need best performance while working with the external data. On the other hand, you should consider linking external data when: The data is too large to be imported into an Access database (~ 2GB). The data is used and changed frequently in the native application. You must share the data over the network with other users. You want to create a multi-user application. Exporting Data You can export data in the same formats as importing data Objects can be tables or queries. You can also export data back to ODBC datasources! 10

17 2.2 ODBC CONNECTIONS 11 ODBC stands for Open Database Connectivity and is a windows interface to establish connections between database applications. History of ODBC Access uses SQL for reading and updating data. Products that speaks SQL should be able to talk to each other. SQL is standardized, but most implementations exhibit variations. Therefore, 30 companies defined a common base SQL implementation so that different SQL-based products could talk to each other Common Language Interface (CLI). Microsoft developed PC CLI and called it ODBC, By the end of 1992, more than a dozen vendors committed to providing ODBC support in their product.

18 2.2 ODBC CONNECTIONS 12 Overview of ODBC ODBC software acts as a bridge between two SQL disparate databases. In order to setup an ODBC connection, an ODBC driver has to be installed. MS Access was one of the first ODBC compliant product.

19 2.2 ODBC CONNECTIONS 13 Use Windows built-in ODBC Driver Manager tool Control Panel System & Performance, Administrative Tools ODBC Data Sources

20 2.2 ODBC CONNECTIONS 14 In Windows 7, 32 bit ODBC Manager is installed under c:\windows\syswow64, search for odbcadm32.exe.

21 2.2 ODBC CONNECTIONS 15 ODBC Administrator Tool is divided into multiple tabs: A user DSN is user specific, that means if a windows login exists, it is only available to that user. A system DSN is user independent meaning anyone having access to the computer where the data source is set up can use this DSN. A file DSN is a portable data source name where the ODBC set up can be copied to other computers or installed on the network. The Drivers tab shows all available drivers installed on the current local computer. You will see both, 32-bit and 64-bit drivers, but you can only use the ones compatible with the launched ODBC Manager (32 or 64-bit).

22 2.2 ODBC CONNECTIONS 16 Creating a Data Source in ODBC Manager To create an ODBC data source, follow these steps: First decide on whether to create a User, System, or File DSN. Select the appropriate DSN tab, and then click Add. Select the installed driver of the target database, and then click on Finish. Configure the data connection, mainly user account and password. Click the Test Connection button. Depending on the ODBC driver, a login dialog box is displayed (example Oracle).

23 2.2 ODBC CONNECTIONS 17 If the connection is successful: If connection did not succeed:

24 2.2 ODBC CONNECTIONS 18

25 Linking External Data 3.

26 3.1 OVERVIEW OF LINKING DATA 19 Linking data into an MS Access database allows you to build powerful application components: Reporting tool to combine data from different sources Front-end application to link to client server database. Multi-user applications linking a shared Access back-end. MS Access is comprised of three different components: Database Engine: Storing and manager data, integrity, indexes. Application Layer: Forms, reports, navigation, but also design interfaces such as table, query, macro designer. Procedural Programming IDE: Automating database applications and processes by using procedural programing language (VBA).

27 3.1 OVERVIEW OF LINKING DATA 20 Use Access as an interface for many database systems. Especially useful for client/server databases.

28 3.1 OVERVIEW OF LINKING DATA 21 To create a linked table, follow these basic steps: Click on the External Data tab. In the Import & Link group, select the desired file format you want to link to. In the first dialog box, select whether to link or import the external data source. Follow the next steps to complete the linked table connection. Once a linked table connection is established, the linked table appears in the Navigation Pane almost like a native table with the exception of a small arrow pointing to the linked table. That arrow indicates that it is a linked table. Hovering the mouse over the linked table allows you to view the linked table connection information

29 3.2 LINKING EXTERNAL DATA 22 You can link to the following file formats: Excel (all versions) (read-only) Access (all versions) (tables only) ODBC databases Text files (read-only, but add records) Share Point Lists Data Services (Share Point Server) HTML Document (read-only) Outlook/Exchange Folder Note that some of these linked connections are read-only depending on the file format. Many file formats are updatable, in general.

30 3.2 LINKING EXTERNAL DATA 23 Selecting the External Data Source First step is to point to external data source. Mostly done with File Open Dialog box, ODBC connections through Manager Tool. Click on Browse. After selecting a data source, additional steps may be necessary. Managing Linked Tables To rename a linked table name, simply select it and right-click on it, then select rename. Note that you are only renaming the linked table name and not the source table name. To delete a linked table, simply select it and press the [Del] key. Again, you are only deleting the linked table in the current database and not the source table in the native system.

31 3.2 LINKING EXTERNAL DATA 24 Linked tables in navigation page display different icons based on file format. In general, you cannot change table Text design properties, except application layer properties maintained by MS Access. You will receive the following Warning message when entering design view of a linked table. ODBC Access dbase Excel Html Properties that can be modified.

32 3.2 LINKING EXTERNAL DATA 25 Updating Data in Linked Tables Not all linked tables are updateable. In general, Excel spreadsheets, text and html files are not updatable, but you can add new records to a linked table based on a text file. Linked MS Access and ODBC tables are potentially updatable, but it depends on how the link is established. Most importantly, the linked table connection in MS Access needs to know the primary key of the source table in order to allow data updates. Under certain circumstances, MS Access can identify the primary key of the source data (depending on ODBC driver) and it will use it when performing data update operations.

33 3.2 LINKING EXTERNAL DATA 26 Using Linked Tables Linked tables in MS Access can be used in the same way as native tables, that is the beauty about linked tables. Queries, forms, and reports can be based on linked tables as well as native tables. Furthermore, you can create queries and include native and linked tables. You must establish a link either in the query or use the relationship builder tool. However, no referential integrity can be enforced, the checkbox is grayed out for any relationship that involves a linked table as shown

34 3.2 LINKING EXTERNAL DATA 27

35 3.2 LINKING EXTERNAL DATA 28

36 3.2 LINKING EXTERNAL DATA 29

37 Importing External Data 4.

38 4.1 OVERVIEW OF IMPORTING DATA 30 When importing data into MS Access you have to consider possible data type differences or mixed data types in one column. Since you can import data from text or spreadsheet files, possible conflicts may exist in terms of data types. When importing data you go through a series of steps that you may want to repeat with a certain frequency, for example to import currency data on a daily basis. For this very reason, the import steps can be saved during the last step of the import wizard. This feature allows you to automate the import process by using a macro or VBA code.

39 4.1 OVERVIEW OF IMPORTING DATA 31 To access the saved imports (and saved exports as well) you click on the Saved Imports button in the External Data tab, Import & Link group. Select the particular saved import and click on the Run button. You can also delete a saved import here as well as create an Microsoft Outlook task.

40 4.1 OVERVIEW OF IMPORTING DATA 32

41 4.1 OVERVIEW OF IMPORTING DATA 33 Besides saving the import steps, for text files only, you can further specify the exact composition and position of text data to be imported. Again, this is for the sole purpose of automating an import process. For example, for fixed-width text data, the exact character positions of all columns in the text file can be defined so that the import process exactly knows how to populate the fields in a table.

42 4.2 IMPORTING EXTERNAL DATA 34 Importing data into MS Access basically means copying data and moving them into MS Access. In addition to importing data, MS Access provides also a tool for importing other objects such as queries, forms, reports, macros, and modules from other Access databases. To import data or objects from another Access database, click on the External Data tab, then in the Import & Link section click on Access. Then the Get External Data Access Database dialog box is displayed to select the file from which data is to be imported and whether to import or link.

43 4.2 IMPORTING EXTERNAL DATA 35 More Objects: Relationships Menus and Toolbars Import/Export Specifications Navigation Pane Groups Images and Themes More Options: Import tables: Definitions and data Definition only Import queries As queries As tables

44 4.2 IMPORTING EXTERNAL DATA 36 Data type conversion takes place when importing data (defined by drivers)

45 4.3 IMPORTING SPREADSHEET DATA 37 MS Access allows importing data from Spreadsheet software such as Excel. However, due to the nature of spreadsheet data (data and text) two conditions must be met to be able to import data into MS Access: The data must be arranged in a table like format (rows and columns) The data must be of the same data type in each column Spreadsheet data can be as selective as named range in a sheet. Column Junk will cause problems because it contains mixed data types. Whenever Access determines that data in column is comprised of different data types, it imports the data as text, if possible. Access determines the data type based on the values it detects in the spreadsheet s first few rows. If the first row contains column headers, that row is excluded from the determination of the data type.

46 4.3 IMPORTING SPREADSHEET DATA 38 Determination of data types If the first couple of rows are not representative of all the data in your spreadsheet, or if you want to force a text data type for number data, then insert a dummy row in your spreadsheet with the desired data type.

47 4.3 IMPORTING SPREADSHEET DATA 39

48 4.3 IMPORTING SPREADSHEET DATA 40

49 4.3 IMPORTING SPREADSHEET DATA 41

50 4.4 IMPORTING TEXT FILES 42 Data from word processing files cannot be imported directly into MS Access. However, most word processors allow you to save a file in a simple text or ASCII format. Additionally, when you need to exchange data between systems where no native or non-native drivers are available, the last option is almost always to export data in some sort of a text format. In order for MS Access to import text data into rows and columns, there must be some indicators in the text file to separate columns of data and rows of data. There are two file types. Delimited Text File Each record is on a separate line in the text file, and the individual elements are separated by a delimiter. In MS Access, you can have the following delimiters: Comma, Tab, Semicolon, Space Furthermore, you can also specify a custom delimiter in MS Access.

51 4.4 IMPORTING TEXT FILES 43 Delimited Text File Fixed-Width Text File There is also one record per line, however, fields are not separated by any special characters. Each data element has a fixed width, if the content of the element is not long enough it is padded with trailing spaces.

52 4.4 IMPORTING TEXT FILES 44

53 4.4 IMPORTING TEXT FILES 45

54 4.4 IMPORTING TEXT FILES 46

55 4.4 IMPORTING TEXT FILES 47

56 4.4 IMPORTING TEXT FILES 48

57 4.4 IMPORTING TEXT FILES 49

58 4.4 IMPORTING TEXT FILES 50

59 4.4 IMPORTING TEXT FILES 51

60 Exporting MS Access Data 5.

61 5.1 OVERVIEW OF EXPORTING DATA 52 Exporting data is very similar to importing data. You basically go through the same steps as with importing data. Particular consideration must be given to the formatting of data as this may or may not be exported out. First of all, besides table data you can also export resulting data from a query into any of the supported file formats including ODBC databases. When exporting to another Access database, you can in addition export all other Access main objects, such as queries, forms, reports, macros, and code modules.

62 5.1 OVERVIEW OF EXPORTING DATA 53 There are some differences compared to the import file formats, i.e. Word Merge file format (delimited text file using tab delimiter). You can also send out an attaching the selected data (either table or query). Default program must be installed. The following file formats are supported natively by MS Access: Three options when exporting: Export data with formatting and layout. Open the destination file after the export operation is complete. Export only selected records.

63 5.1 OVERVIEW OF EXPORTING DATA 54 When you export data, you have to understand the export takes place at the database level. Certain properties in table and query design are not part of the database, they are part of the application layer part in Access. A good example is the format property. The database does not know anything about this property, it will export only the actual data. Input Mask: Store mask in database or not, if stored then it is exported. You can use functions to convert and/or format data before you export it, this way you have control exactly what data is exported and how it is formatted.

64 5.2 EXPORTING DATA 55

65 5.2 EXPORTING DATA 56

66 5.2 EXPORTING DATA 57

67 5.2 EXPORTING DATA 58

68 Linking MS Access Tables 6.

69 6.1 OVERVIEW OF LINKING DATA 59 Besides linking other file format-based tables into an Access database, you can also link an Access table or tables to another Access database. Why not import other Access data into the same file? Reasons for splitting Access databases: One reason might be that one Access application resides in a different location, such as a network drive where users can access it. Another reason might be file size, an Access database can be up to 2GB in size. The last reason is probably the most common, and that is to create a multi-user application. MS Access is a file-based database product, meaning it cannot split its CPU processing tasks across different physical computers. You can split database files and link tables into an Access database, but the processing tasks are executed in the CPU on the computer where you are running MS Access.

70 6.2 ARCHITECTURE OF MULTI-USER ACCESS APPS 60 Split Access into two components: Front-end: The application interface of the database application, mainly forms, reports and navigation. Back-end: The database tables. The front-end file contains the linked tables that point to the tables in the back-end file. The front-end contains queries, forms, reports, and modules. Furthermore, the front could also include tables, such as lookup tables where data is not changed. The back-end data database contains only tables and the established relationships.

71 6.2 ARCHITECTURE OF MULTI-USER ACCESS APPS 61 If MS Access is run on a client computer, all the CPU processing is performed on that computer. For example, running a query against a table with 100,000 records with a criterion limiting the number of records to 10 still requires the entire table to be moved over the network (a file is served to the client) to the client where the query is processed. Client/server databases process database task on a database server and send the result to the client (in this example only 10 records), which results in a dramatic reduction of network traffic. The main benefits of splitting MS Access databases are: Sharing data over a network server, thereby creating a multi-user application Many users can update data at the same time Updating the front-end part is much easier because the data back-end remains untouched.

72 6.3 SPLITTING AN ACCESS DATABASE 62 To create a multi-user application, the transaction tables must be moved to a separate Access database *.accdb file. Database Splitter Tool You can also manually perform the splitting of a database into a front-end and a back-end: Create a new, blank database in MS Access and name it MyApp_be.accdb. Copy initial database into MyApp_fe.accdb (that automatically preserves the initial file). Import transaction tables from MyApp_fe.accdb into MyApp_be.accdb. Delete all transaction tables in MyApp_fe.accdb. Link all transaction tables from MyApp_be.acdb into MyApp_fe.accdb.

73 6.3 SPLITTING AN ACCESS DATABASE 63

74 6.3 SPLITTING AN ACCESS DATABASE 64

75 6.3 SPLITTING AN ACCESS DATABASE 65

76 6.4 LINKED TABLE MANAGER 66 Three main purposes: You can view all your linked tables in one view including the connection information. You can refresh linked tables in case the source table s definition has changed (columns, indexes, etc.). You can switch your front-end Access application to a different back-end database. Navigate to the External Data tab in the ribbon, and then click on Linked Table Manager to access this tool. You can individually select the linked table to be updated by clicking in the checkbox, and then click on OK. Use the buttons Select All or Deselect All to check/uncheck all linked tables. If the linked table(s) connection is valid, MS Access will display a dialog box that all table links are refreshed.

77 6.4 LINKED TABLE MANAGER 67 Refreshed Linked Tables Confirmation There are three possible scenarios when a link to an external data source is not valid anymore: Database/file was moved to a different location, but table names have not changed. Database/file is in original location but individual table name has changed. Database/file name has changed. For invalid linked tables, the File Open Dialog box is displayed automatically.

78 6.4 LINKED TABLE MANAGER 68 Note that the title bar of this dialog box contains the table name currently being selected and in the process of being refreshed. Select the table and click on Open. After successfully refreshing the linked table, the confirmation dialog box is displayed. To switch linked tables to a different location, even though the current link is valid, select the checkbox at the bottom of the Linked Table Manager dialog box named Always prompt for a new location. Development front-end is linked to test back-end data. When front-end is moved to production, point to production back-end.

79 6.5 SETTING UP MULTI-USER APPLICATIONS 69

80 6.5 SETTING UP MULTI-USER APPLICATIONS 70

81 6.5 SETTING UP MULTI-USER APPLICATIONS 71