INDEX. 1 Introduction. 2 Types of Cursors 2.1 Explicit cursor 2.2 Attributes 2.3 Implicit cursor 2.4 Attributes. 3 Parameterized cursor

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1 INDEX 1 Introduction 2 Types of Cursors 2.1 Explicit cursor 2.2 Attributes 2.3 Implicit cursor 2.4 Attributes 3 Parameterized cursor

2 INTRODUCTION what is cursor? we have seen how oracle executes an SQL statement. Oracle DBA uses work area for its internal processing. This work area is private to SQL's operations and is called as "cursor". The data that is stored in the cursor is called a Active Data Set. The size of cursor in the memory is the size required to hold the numbers rows in the active data. 2

3 Example:- when a users fires a select statement as, select empno, ename, job, salary from employee where deptno=20; the resuitant data set will be as displayed in diagram, Active Data Set empno ename job salary 3456 SUMIT MANAGER PRADEEP ANALYST MITESH PROGRAMER VIJAY CLERK SACHIN ACCOUNTANT 3000

4 EXPLICIT CURSOR:- You can explicitly declare a cursor to process the rows individually. A cursor declared by the user is called "Explicit cursor" Why use an explicit cursor? Cursors can be used when the users wants to process data one row at a time. To do the via a PL\SQL block it is necessary to declare a cursor and associate it with a query before referencing it in any statement within the PL\SQL block. This is beacuse forward references to objet are not allowed in PL\SQL. CURSOR cursorname IS DECLARING A CURSOR:- Syntax:- Example:- SQL statement DECLEAR cursor c_emp is select emp_code, salary from employee where deptno=20; 4

5 OPENING A CURSOR:- Opening the cursor executes the query and identifies the active set, that contains all the rows which meet the query search criteria. Syntax:- OPEN cursorname; Example:- DECLARE cursor c_emp is select emp_code, salary from employee where deptno=20; BEGIN *Opening cursor c_emp*/ open c_emp; END;

6 CLOSING A CURSOR:- The close statement disables the cursor and the active set becomes undefined. This will release the memory occupied by the cursor and it's data set. Syntax:- CLOSE cursorname; Example:- DECLARE cursor c_emp is selected emp_code,salary from employee where deptno=20; str_emp_code employee.emp_code%type; num_salary employee.salary%type; BEGIN open c_emp; loop fetch c_emp into str_emp_code,num_salary; update employee set salary=num_salary+(num_salary*.05) where emp_code=str_emp_code; end loop; close c_emp; END;

7 Explicit cursor Attributes:- %NOTFOUND:- Evaluate to true, if the last fetch has failed because no more rows were available; OR to false, if the last fetch returned a row. Syntax:- cursorname%notfound %FOUND: - is the logical opposite of that both attributes evaluate to null they are set by an implicit cursor operation.% found evaluates to true, if an insert, update or delete affected one or more rows, or a single-row select returned one or more rows. Otherwise, it evaluates to false. Syntax: SQL%FOUND

8 %ISOPEN:- evlauates to true. if an explicit cursor is open; or false, if it closed. syntax: cursorname%isopen %ROWCOUNT:- return the number of rows fetched from the active set. It is set to zero when the cursor is open. syntax:- cursorname%rowcount

9 IMPLICIT CURSOR:- Oracle implicitly opens a cursor to process each SQL statement not associated with an explicitly declared cursor. PL/SQL lets you refer to the most recent implicit cursor as the SQL cursor. so, although you cannot use the open, fetch, and close statements to control an implicit cursor, you can still use cursor attributes to access information about the most recently executed SQL statement. Implicit cursor Attributes:- The SQL cursor has four attributes as described below. When appended the cursor name(i.e. SQL), these attributes let you access information about the execution of insert, update, delete and single-row select statements. Implicit cursor attributes return the Boolean null value, until they are set by a cursor operation.

10 %NOTFOUND:- Evaluates to true, if an insert, update or delete affected no rows,or a single-row select returns no rows.otherwise,it evaluates to false. Syntax:- SQL%NOTFOUND %FOUND:- is the logical opposite of that both attributes evaluate to null they are set by an implicit cursor operation.% found evaluates to true, if an insert, update or delete affected one or more rows, or a single-row select returned one or more rows. Otherwise, it evaluates to false. Syntax:- SQL%FOUND

11 %ROWCOUNT:- return the number of row affected by an insert,update or deleted,or select into statement. %ISOPEN:- Oracle automatically close the cursor after executing the associated SQL statement. as a result sql % isopen always evaluate to false.

12 PARAMETERIZED CURSORS:- SO far we have used cursors querying all the record from the table. sometimes record are brought selectively. while declaring a cursor the selected statement must include a where clauses to retrieve data conditionally. we should able to pas a value to cursor only when it being opened for that the cursor must be declared in such a way that it recognize that it will receive the request value(s) at the time of opening the cursor. such a cursor is known as parameterized cursor. syntax:- CURSORcursor_name(variable_name data type)is select statement.

13 Example:- cursor c_(num_deptno number)is select job, ename from emp where deptno>num_deptno; The parameter of a cursor can be passed in a open statement. they can either be constant values or of the content of a memory variable for example OPEN C_emp(30) OPEN C_emp(num_deptno)