June 7th Thursday
3
1. We cannot change SQL statements associated to it. 2. We cannot pass explicit cursor as a parameter between subprograms. Write a PL/SQL block for displaying information from emp table for any where condition { select * from emp where &condition } In such situations we use REF Cursor or cursor variable or dynamic cursor: ----------------------------------------------------------- We can change the condition during the program execution. Using a ref cursor is a two step process. 1. Declare a variable of type REF cursor. Syntax: type <typename> is REF cursor [return <datatype>]; Ex: type a is ref cursor r eturn emp%rowtype; -- If we specify return t ype then it is called as strongly typed cursor or constrained cursor. type b is ref cursor; -- Week cursor or unconstrained cursor 2. Declare a variable of type declared in above step. Ex: x a; -- x is cursor variable of type a ... with return emp%rowtype. y b; -- y is cursor variable of t ype b 3. Open the step two variables for any select statement... Syntax: open <cursorvariable> for <selectstatement>; Ex: open x for 'select * from emp where deptno=10'; open y for 'select empno,ename,sal,comm from emp where job=''CLERK'''; 4. Process cursor variable similar to explicit cursor. Note: We cannot use cursor for loop for these ref cursors.
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Transcript of June 7th Thursday
7/31/2019 June 7th Thursday
http://slidepdf.com/reader/full/june-7th-thursday 1/3
1. We cannot change SQL statements associated to it.
2. We cannot pass explicit cursor as a parameter between subprograms.
Write a PL/SQL block for displaying information from emp table for any where condition
{
select * from emp
where &condition
}
In such situations we use
REF Cursor or cursor variable or dynamic cursor:
-----------------------------------------------------------
We can change the condition during the program execution.
Using a ref cursor is a two step process.
1. Declare a variable of type REF cursor.Syntax:
type <typename> is REF cursor [return <datatype>];
Ex:
type a is ref cursor return emp%rowtype; -- If we specify return type then it is called as strongly typed
cursor or constrained cursor.
type b is ref cursor; -- Week cursor or unconstrained cursor
2. Declare a variable of type declared in above step.
Ex:
x a; -- x is cursor variable of type a ... with return emp%rowtype.
y b; -- y is cursor variable of type b
3. Open the step two variables for any select statement...
Syntax:
open <cursorvariable> for <selectstatement>;
Ex:
open x for 'select * from emp where deptno=10';
open y for 'select empno,ename,sal,comm from emp where job=''CLERK''';
4. Process cursor variable similar to explicit cursor.
Note: We cannot use cursor for loop for these ref cursors.
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set serveroutput on
declare
type a is ref cursor;
x a;
condition varchar2(1000) := '&condition';
slstmt varchar2(1000);
i emp%rowtype;
begin
sqlstmt:= 'select * from where' || condition;
open x for sqlstmt; -- opening a cursor variable for sql statement
loop
fetch x into i;
exit when x%notfound;
dbms_output.put_line('Ename is ' || i.ename);
end loop;
close x;
end;
set serveroutput on
declare
x sys_refcursor; -- sys_refcursor is a builtin ref cursor variable
condition varchar2(1000) := '&condition';
slstmt varchar2(1000);
i emp%rowtype;
begin
sqlstmt:= 'select * from where' || condition;
open x for sqlstmt; -- opening a cursor variable for sql statement
loopfetch x into i;
exit when x%notfound;
dbms_output.put_line('Ename is ' || i.ename);
end loop;
close x;
end;
Write a PL/SQL block for displaying number of columns in a given table.
set serveroutput on
declare
type a is ref cursor;
x a;
col_count number(2);
slstmt varchar2(1000);
v_tab_name varchar2(32):= '&tabname';
begin
sqlstmt:='select count(*) from user_tab_column where table_name =' || v_tab_name;
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open x for sqlstmt;
loop
fetch
-------------------
-------------------
-------------------
IMPLICIT CURSOR:
-----------------------
"SQL" -- DML (i/u/d)
SQL%ISOPEN -- FALSE
SQL%FOUND
SQL%NOTFOUND
SQL%ROWCOUNT -- Given the information about number of rows effected.
HW ASSIGN:
Write small notes about SQL%FOUND
SQL%NOTFOUND
