D a t a b a s e M a n a g e m e n t S y s t e m L a b Institute of Engineering and Management

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1 Institute of Engineering and Management Department of Computer Science and Engineering Database Management Laboratory (CS 691) Lab Manual

2 Syllabus: Database Management System Lab Code: CS691 Contact: 3P Credits: 2 Structured Query Language 1. Creating Database Creating a Database Creating a Table Specifying Relational Data Types Specifying Constraints Creating Indexes 2. Table and Record Handling 1. INSERT statement 2. Using SELECT and INSERT together 3. DELETE, UPDATE, TRUNCATE statements 4. DROP, ALTER statements 3. Retrieving Data from a Database The SELECT statement Using the WHERE clause Using Logical Operators in the WHERE clause Using IN, BETWEEN, LIKE, ORDER BY, GROUP BY and HAVING Clause Using Aggregate Functions Combining Tables Using JOINS Subqueries 4. Database Management Creating Views Creating Column Aliases Creating Database Users Using GRANT and REVOKE

3 Oracle Class 1 Covers overview of tables and assignment of first day. Data What is data? What is quantitative and qualitative data? What is metadata? What is structured data, unstructured data? <?xml version="1.0"?> <catalog> <book id="bk101"> <author>gambardella, Matthew</author> <title>xml Developer's Guide</title> <genre>computer</genre> <price>44.95</price> <publish_date> </publish_date> <description>an in-depth look at creating applications with XML. </description> </book>

4 SQL SQL DDL DML DCL TCL Select Insert Update Delete select * from test; select temp from test insert into test values (4,200,'string values') update test set temp='dummy text' where temp is null delete from test where id = 3 Grant, Revoke Set transaction, commit, rollback Table

5 Create Table Create Table <Tablename> { <column name> <datatype> <constraints>,. } Simple Form : SQL> create table test ( id integer, name varchar2(50) ); Create Table Adding constraints SQL> create table test1 ( id integer not null, age integer default 25, name varchar2(50) ); Other options We can add a primary key ( There are 5 type of constraint Primary Key, Foreign Key, Not Null, Unique and Check ) We can use ENCRYPT clause We can give option as GENERATED ALWAYS AS

6 Primary Key, Foreign Key constraint create table empl ( id integer primary key, age integer default 25, name varchar2(50) ); create table dpndnt ( id integer primary key, age integer default 25, name varchar2(50), eid integer not null CONSTRAINT dpndnt_fkey REFERENCES empl(id) ); A primary key value cannot be null All primary key values must be unique within a column Primary key values can optionally be paired with a corresponding foreign key value in another table, forming a relationship it can be mentioned as inline or as a constraint at the end Altering a table Modifying a datatype Alter table test1 Modify name varchar2(100); Adding a Column Alter table test1 Add extra char(10); Dropping a Column Alter table test1 Drop column extra char(10); Adding or changing constraint alter table empl modify name not null;

7 Metadata, data dictionary desc <tablename> ; user_tables - > Gives details about the tables User_tab_columns -> Gives details about the columns Assignment - Complete schema design for a student attendance system - It should have entity for class, student, subject, routine, attendance - Create proper primary key and foreign keys - Write notes on Temporary table and Global Temporary table - Give an example where CATS will be necessary, with necessary syntax - Give a listing of the tables, columns and constraints

8 Oracle Class I1 Overview of select, insert, update, delete Contains class II assignments SELECT SELECT [DISTINCT UNIQUE] (*, columnname [ AS alias], ) FROM tablename [WHERE condition] [GROUP BY group_by_expression] [HAVING group_condition] [ORDER BY columnname];

9 Select Contd Selecting all columns using * Selecting some of the columns -> Projection Alias names if contains space or special symbol, then it needs to be put in double quotes Distinct and unique can be used to remove duplicates comparison operators =;!= or <>; <; >;<=, => are allowed in the conditions of a where clause. One useful query to get the number of queries is count(*) Order by, by default gives result in ascending order For string type of data like can be used. is used as a concatenation operator for strings and string literal is to be enclosed within single quotes. Select Contd Multiple conditions can be concatenated using and or etc for range queries we can use between and. Example : Select to, from where size between 10 and 20; IN for multiple values Select city, population from citydetails where city in ( kol, mum, del, chn ); Similarly not in can be used Like to be used for pattern matching a%, %a% and %a An input value can be taken form the user, using and & select * from dept where deptno=&no;

10 Select Contd Multiple conditions can be concatenated using and or etc for range queries we can use between and. Example : Select to, from where size between 10 and 20; IN for multiple values Select city, population from citydetails where city in ( kol, mum, del, chn ); Similarly not in can be used Like to be used for pattern matching a%, %a% and %a An input value can be taken form the user, using and & select * from dept where deptno=&no; Case sensitivity, whitespace, terminators SQL commands have the same meaning whether used with uppercase or lowercase characters various SQL elements, or "words", must be separated by whitespace (usually a "space" character), the use of extra spaces, tabs, and end-of-line character has little effect on the syntactical correctness of the statement. In Oracle SQL, two statement terminators can be used; the semicolon (;) and the forward slash (/). The two are similar in their use, the main difference being that the forward slash can only be used on a separate line. Aliasing: select dname as "Departmentname", loc as "Location" from dept;

11 Assignments write query to select all the columns of emp table write query to select only Empname, Ename and Job write query to select unique Jobs write query to select only those employees who are salesman select employee name, grade and salary, in the order of their salary Mgmt is considering a pay raise, however they want to find out, if they give a flat 200$ increment to all, then what % each person is getting. So in your result display, ename, salary and pctincr Express work experience of each of the employeses by using sysdate and hiredate in terms of no of years. Hints : you would need to use cast

12 Assignments contd. select only those employees who are a clerk and a manager. Use all of or condition, IN and NOT IN clause Comment on the case sensitivity of the string literal within single quote use emp table and use different columns and string concatenation to display a message like below for each of the employees Output Example : JAMES is a CLERK and is working in the company for last 32 Years use emp table to display only those employees who have joined in the year 80 and 81. Comment on if between clause is inclusive or exclusive Assignments contd. Use like statement to display name of the employees which start with A Write your remarks on use of wildcards with like statement Select those employees, who has joined on or before 31 st December 1982 and is either a clerk or having a salary greater than 2500

13 Oracle Class III Group by, Having Insert/Update/Delete System Functions Set Operators Group By Select <column(s)> from <table(s)> [where <condition>] group by <group column(s)> [having <group condition(s)>]; The result will return # rows based in the group columns, basically based on distinct combination of group by columns Some aggregate functions needs to be used on the columns. Example : Sum, Avg, Min, Max, count(*) etc Having is used to restrict some of the groups appearing in the result

14 Insert/Update/Delete Insert into <table> [(<column i, : : :, column j>)] values (<value i, : : :, value j>); For each of the listed columns, a corresponding (matching) value must be specified. Insertion does not necessarily have to follow the order of the attributes as specified in the create table statement If a column is omitted, the value null is inserted instead update <table> set <column i> = <expression i>, : : :, <column j> = <expression j> [where <condition>]; delete from <table> [where <condition>]; Case conversion,string String Functions Upper Lower Initcap Length Lpad Rpad Rtrim Ltrim Concat substr instr SUBSTR(column_expression, start position, end position) INSTR(column_expression, search_character, starting_position, occurrence_number) Lpad/Rpad (Column, length,padding column)

15 Date functions, conditions Current _timestamp is a pseudo column like sysdate Month_between ( Start date, end date ) Add_months ( Date, no of months) Decode (Column, condition, value, condition, value ) It can be if and else if, else it can be else it can be if and else if, in this case for no match null is returned DECODE(E1, E2, E3, E4) IF E1 = E2 THEN E3 ELSE E4 NULLIF(E1, E2) IF E1 = E2 THEN NULL ELSE E1 NVL(E1, E2) IF E1 IS NULL THEN E2 ELSE E1 NVL2(E1, E2, E3) IF E1 IS NULL THEN E3 ELSE E2 CASE WHEN C1 THEN R1 WHEN C2 THEN R2... WHEN CN THEN RN ELSE RD END Set operators Set operators can be used to combine records from multiple tables Different operators are union, union all, intersect, minus respectively Union removes the duplicates, where as union all does not Both the sets need to have the same no of columns and compatible datatypes

16 Oracle Class IV Joins Subquery Join A join query extracts information from two or more tables or views. A join query differs from a regular query in at least the following two ways: The FROM clause of a join query refers to two or more tables or views. A condition is specified in the join query (known as join condition) that relates the rows of one table to the rows of another table. SELECT departments.location_id, departments.department_name, locations.state_province FROM departments JOIN locations ON departments.location_id = locations.location_id;

17 Type of Joins Inner Join : Inner joins are the regular joins. An inner join returns the rows that satisfy the join condition. Outer Join : Outer joins are an extension to inner joins. An outer join returns the rows that satisfy the join condition and also the rows from one table for which no corresponding rows (i.e., that satisfy the join condition) exist in the other table. FROM table1 { LEFT RIGHT FULL } [OUTER] JOIN table2 Left Outer join : Right Outer Join Full outer Join Cartesian join or cross join when you don't specify a join condition when joining two tables Self joins A self join is a join of a table to itself. Equi- and non-equi-joins An equi-join is a join where the join condition uses the equal to (=) operator to relate the rows of two tables Other points of join Oracle proprietary syntax is different, inner join is written in table 1, table 2 where table 1.columnname= table2.columnname. A + sign is used to indicate an outer join SELECT FIRSTNAME, LASTNAME, PROJECTNAME FROM EMPLOYEE E, PROJECT P WHERE E.PROJECT_ID(+)=P.PROJECT_ID

18 Subquery A subquery is simply a query that is nested inside another query or a nested query The nested query, sometimes referred to as an inner query, is evaluated first, and its resulting data set is passed back to the outer query and evaluated to completion. Subqueries can be effectively used in situations where the combined data has no direct relationship as compared to joins scalar or single-row subqueries :The subquery returns a single value to the outer query Scaler subqueries can be used for both where and having clause. Subqueries are most often found in the WHERE clause of a SELECT, UPDATE, or DELETE statement Ex : Select name of the employees other than Kevin Feeney who gets the same salary as Kevin Non correlated subquery Noncorrelated subqueries allow each row from the containing SQL statement to be compared to a set of values. The nested query, sometimes referred to as an inner query, is evaluated first, and its resulting data set is passed back to the outer query and evaluated to completion. Subqueries can be effectively used in situations where the combined data has no direct relationship as compared to joins scalar or single-row subqueries :The subquery returns a single value to the outer query Scaler subqueries can be used for both where and having clause.

19 Correlated subquery A correlated subquery is a subquery that uses values from the outer query, requiring the inner query to execute once for each outer query With a correlated subquery, the database must run the subquery for each evaluation because it is based on the outer query s data. select book_key, store_key, quantityfrom sales s Where quantity < (select max(quantity) from sales where book_key = s.book_key); SELECT S.Number, S.Name FROM Salesman S WHERE S.Number IN (SELECT C.Salesman FROM Customer C WHERE C.Name = S.Name) Non correlated and correlated subquery contd. Noncorrelated subqueries allow each row from the containing SQL statement to be compared to a set of values. Single-row, single-column subqueries Multiple-row, single-column subqueries Multiple-column subqueries SELECT lname FROM employee WHERE salary > (SELECT AVG(salary) FROM employee); SELECT fname, lname FROM employee WHERE dept_id = 30 AND salary >= ALL (SELECT salary FROM employee WHERE dept_id = 30); SELECT fname, lname FROM employee WHERE dept_id = 30 AND NOT salary < ANY (SELECT salary FROM employee WHERE dept_id = 30);

20 Assignments Display name of employees, department name and job name for each employee Display the department name along with no of employees and average salary of that department For each department, find out no. of jobs the employees are assigned to. Check for correctness of the above queries in terms of count, if you want to bring in all entries, how would you achieve the same? Group by the employees based on the first character of employee first name. Display the results in alphabetic order (descending) of first character. Display name of those employees who get a salary more than the average salary Display name of the all the employees who are stock manager, except the one who gets the minimum salary. Assignments contd. Display firstname,lastname,salary of those sales representatives who earns a higher salary than the minimum salary a sales manager receives. Display the name of the employees/employee who gets the second highest salary. (sub query) Come up with the query for previous question using set operators Display the name of the employee (manager) who has the maximum no. of employees reporting to him. Display the name of those employees, who are in the same department as Timothy Gates and gets an salary more than the average salary of all the employees

21 Assignments contd. If an employee have spent less than 5 years then he is considered entry level id 5 10 then midlevel else a senior employee. Write a query, which will label the employees in either of the above categories Write query to find out any departments that are present in department table but does not have employees Write a query which will display job id, which are present in both job and employee columns Increase salary of each employee of all the department who draws the minimum salary by 100$.

22 Oracle Class V PL/SQL basics Architecture

23 Single Unit What Is PL/SQL? PL/SQL is a procedural programming language from Oracle that combines the following elements: Logical constructs such as IF-THEN-ELSE and WHILE SQL DML statements, built-in functions, and operators Transaction control statements such as COMMIT and ROLLBACK Cursor control statements Object and collection manipulation statements

24 A simple PL/SQL block The Declaration section (optional) The Declaration section of a PL/SQL Block starts with the reserved keyword DECLARE. This section is optional and is used to declare any placeholders like variables, constants, records and cursors The Execution section (mandatory). The Execution section of a PL/SQL Block starts with the reserved keyword BEGIN and ends with END. This is a mandatory section and is the section where the program logic is written to perform any task. The programmatic constructs like loops, conditional statement and SQL statements form the part of execution section. The Exception (or Error) Handling section (optional) The Exception section of a PL/SQL Block starts with the reserved keyword EXCEPTION. This section is optional. Any errors in the program can be handled in this section, so that the PL/SQL Blocks terminates gracefully. Example - procedure DECLARE v_sal numeric(7,2); v_ename varchar(10); BEGIN SELECT max(sal) INTO v_sal FROM emp; SELECT ENAME INTO V_ENAME from emp WHERE SAL=V_SAL; DBMS_OUTPUT.PUT_LINE (v_ename ' gets highest salary of ' v_sal ); END; /

25 Example - function CREATE OR REPLACE FUNCTION getmaxval (tnamevarchar2, cnamevarchar2) RETURN NUMBER IS query_strvarchar2(1000); maxval NUMBER; BEGIN query_str := 'SELECT max(' cname ') FROM ' tname; EXECUTE IMMEDIATE query_str INTO maxval; RETURN maxval; END; /` Class Assignment : Create a function which takes two parameters tablename and columnname and returns second max value of the columns.

26 Oracle Class VI Exception Block Cursors For Loops Pl/sql some more basics Loop through records, manipulating them one at a time. Keep code secure by offering encryption, and storing code permanently on the server rather than the client. Handle exceptions. Work with variables, parameters, collections, records, arrays, objects, cursors, exceptions, BFILEs, etc. Pl/SQL is first compiled and stored and then interpreted Reminder : use of ed

27 Exception blocks CREATE OR REPLACE FUNCTION getname (vsal number) RETURN varchar2 IS query_strvarchar2(1000); vename varchar2(100); BEGIN query_str := 'SELECT ename FROM emp' ' where sal= ' vsal; EXECUTE IMMEDIATE query_str INTO vename; query_str := vename ' gets ' vsal; RETURN query_str; EXCEPTION WHEN NO_DATA_FOUND THEN END; / RETURN 'NOT FOUND'; Packages Stored functions and procedures may be compiled individually, or they may be grouped together into packages. Packages are loaded into memory as a whole, increasing the likelihood that a procedure or function will be resident in memory when called. Packages can include private elements, allowing logic to be hidden from view. Placing functions and procedures inside packages eliminates the need to recompile all functions and procedures that reference a newly recompiled function/procedure. Function and procedure names may be overloaded within packages, whereas standalone functions and procedures cannot be overloaded.

28 Loops DECLARE v_count PLS_INTEGER := 0; BEGIN LOOP DBMS_OUTPUT.PUT_LINE('Ah -- Much better'); v_count := v_count + 1; EXIT WHEN v_count = 20; END LOOP; END; / FOR counter IN low_number.. high_number LOOP action; END LOOP; WHILE condition LOOP action; END LOOP; For Loop and DECLARE i NUMBER := 5; BEGIN FOR i IN 1..3 LOOP DBMS_OUTPUT.PUT_LINE ('Inside loop, i is ' TO_CHAR(i)); END LOOP; DBMS_OUTPUT.PUT_LINE ('Outside loop, i is ' TO_CHAR(i)); END; / DECLARE v_count PLS_INTEGER := 1; BEGIN WHILE v_count <= 20 LOOP DBMS_OUTPUT.PUT_LINE('While loop iteration: ' v_count); v_count := v_count + 1; END LOOP; END;

29 Cursor A cursor provides a subset of data, defined by a query, retrieved into memory when opened, and stored in memory until the cursor is closed. If data is added, deleted, or modified after the cursor is opened, the new or changed data is not reflected in the cursor result set. Declaration of a cursor: CURSOR author_cur1 IS SELECT rowid FROM authors WHERE id > 50; Opening a cursor OPEN author_cur1; Cursor Contd. Use a cursor in a loop Opening a loop: LOOP Fetch: FETCH auth_cur INTO v_first_name, v_last_name, v_book_count; Exit: EXIT WHEN auth_cur%notfound; End Loop END LOOP; Close Cursor CLOSE auth_cur;

30 Example of a simple cursor CREATE OR REPLACE PROCEDURE compile_warning AS v_title VARCHAR2(100); CURSOR dbms_warning_cur IS SELECT title FROM books; BEGIN OPEN dbms_warning_cur; LOOP FETCH dbms_warning_cur INTO v_title; EXIT WHEN dbms_warning_cur%notfound; DBMS_OUTPUT.PUT_LINE('Titles Available: ' v_title); END LOOP; CLOSE dbms_warning_cur; END;

31 Oracle Class VII More on Execption Sequence Triggers RowID & Rownum Views Exception Differentiate error and exception More example : EXCEPTION WHEN ZERO_DIVIDE THEN DBMS_OUTPUT.PUT_LINE ('A number cannot be divided by zero.'); VALUE_ERROR :- When there is conversion or type mismatch error. TOO_MANY_ROWS: This exception is raised when a SELECT INTO statement returns more than one row. You can declare your own exception DECLARE e_exception1 EXCEPTION; BEGIN RAISE e_exception1

32 Sequence An Oracle sequence is an Oracle database object that can be used to generate unique numbers. You can use sequences to automatically generate primary key values. After a sequence has been created, you can access its values in SQL statements with these pseudocolumns:. CURRVAL returns the current value of the sequence.. NEXTVAL increments the sequence and returns the new value We can use a maxvalue or minvalue to indicate the maximum value a trigger can have CYCLE is used to indicate, if maxvalue is reached, then the values will be cycled (NOCYCLE by default) Example of sequence: CREATE SEQUENCE trig_seq START WITH 1; CREATE SEQUENCE trig_seq1 START WITH 1 INCREMENT BY 1; CREATE SEQUENCE trig_seq2 START WITH 1 INCREMENT BY 1 maxvalue 255; Example of using a sequence: INSERT INTO test01 VALUES (trig_seq.nextval); Triggers A database trigger is a named PL/SQL block stored in a database and executed implicitly when a triggering event occurs. The act of executing a trigger is called firing the trigger. Four types of triggering events :- A DML statement (such as INSERT, UPDATE, or DELETE) executed against a database table. Such a trigger can fire before or after a triggering event. A DDL statement (such as CREATE or ALTER) executed either by a particular user against a schema or by any user. A system event such as startup or shutdown of the database. A user event such as logon and logoff

33 Trigger continued CREATE [OR REPLACE] TRIGGER Ttrigger_name {BEFORE AFTER} Triggering_event ON table_name [FOR EACH ROW] [FOLLOWS another_trigger] CREATE OR REPLACE TRIGGER student_bi BEFORE INSERT ON students FOR EACH ROW DECLARE sid int; BEGIN select max(stid)+1 into sid from students; dbms_output.put_line('hello'); :new.stid:=sid; END; / FOR EACH ROW WHEN (NVL(NEW.ZIP, ' ') <> OLD.ZIP) RowId & Rownum For each row in the database, the ROWID pseudocolumn returns the address of the row. Use of Rowid: They are the fastest way to access a single row. They can show you how the rows in a table are stored. They are unique identifiers for rows in a table. For each row returned by a query, the ROWNUM pseudocolumn returns a number indicating the order in which Oracle selects the row from a table or set of joined rows. The first row selected has a ROWNUM of 1, the second has 2, and so on.

34 Views Use the CREATEVIEW statement to define a view, which is a logical table based on one or more tables or views. A view contains no data itself. The tables upon which a view is based are called base tables. create view emp10 As select * from emp where deptno=10; View can be created using join on multiple table create view empbonus (ename,sal,job,comm,deptno) as select a.ename,a.sal,a.job,b.comm, a.deptno from emp a inner join bonus b on a.ename=b.ename / Assignments Modify the procedure that takes salary and returns the name, handle the exception so that if user gives a nonnumeric value this exits gracefully. Create a table books, which has columns as bookid and bookname. Insert two rows with booknames database fundamentals and database technologies. Use a sequence to populate the bookid for both the rows. There is a circular from federal govt. no employees can get salary less than 1000$. So in case some employees are being inserted in the table with salary less than 1000 automatically this should be updated to 1000, Write a trigger for the same. Do it first by a just changing the below in insert before, and also by an update command after insert is done. Create a trigger on emp table such that when a new employee is inserted with a deptno that is new, first insert that record in department and then insert the same in emp to avoid foreign key error. Create a view, which hides the salary column from the user. Cerate a view which has ename and dname respectively, check if you can update/insert into the views, justify your results

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