PL/SQL Cursor Properties and Limits on the Number of Cursors

a cursor attribute

%found: the cursor found the record is true

%notfound: true if the cursor did not find the record

%isopen: determine whether the cursor is open

%rowcount: The number of rows affected

 

Two examples

Demonstrate the %isopen property

1. Code

1. set serveroutput on
2. declare
3. --定义光标
4. cursor cemp isselect empno,empjob from emp;
5. pempno emp.empno%type;
6. pjob emp.empjob%type;
7. begin
8. open cemp;
9. if cemp%isopen then
10. dbms_output.put_line('光标已经打开');
11. else
12. dbms_output.put_line('光标没有打开');
13. endif;
14. close cemp;
15. end;
16. /

2. Running results

Cursor is already open

 

PL/SQL procedure completed successfully.

 

Demonstration of the %rowcount property

1. Code

1. set serveroutput on
2. declare
3. --定义光标
4. cursor cemp isselect empno,empjob from emp;
5. pempno emp.empno%type;
6. pjob emp.empjob%type;
7. begin
8. open cemp;
9. loop
10. --取出一条记录
11. fetch cemp into pempno,pjob;
12. exitwhen cemp%notfound;
13. --打印rowcount的值
14. DBMS_OUTPUT.PUT_LINE('rowcount:'||cemp%rowcount);
15. end loop;
16. close cemp;
17. end;
18. /

2. Running results

rowcount:1

rowcount:2

rowcount:3

rowcount:4

rowcount:5

rowcount:6

rowcount:7

rowcount:8

rowcount:9

rowcount:10

rowcount:11

rowcount:12

rowcount:13

rowcount:14

 

Three-cursor limit

1. Concept

By default, the oracle database only allows 300 cursors to be opened in the same session

Cursor limit viewing method:

1. SQL> show parameter cursor
3. NAME TYPE VALUE
4. -----------------------------------------------------------------------------
5. cursor_sharing string EXACT
6. cursor_space_for_time boolean FALSE
7. open_cursors integer 300
8. session_cached_cursors integer 50

Modify the limit on the number of cursors:

alter system set open_cursors = 400 scope=both;

the value of scope

both: Change the current instance and also change the parameter file.

memory: Only the current instance is changed, not the parameter file.

spfile: Only the parameter file is changed, but the current instance is not changed. The database needs to be restarted.

2. Examples

1. SQL> alter system set open_cursors =400 scope=both;
3. 系统已更改。
5. SQL> show parameter cursor
7. NAME TYPE VALUE
8. -----------------------------------------------------------------------------
9. cursor_sharing string EXACT
10. cursor_space_for_time boolean FALSE
11. open_cursors integer 400
12. session_cached_cursors integer 50