Oracle- creating dynamic function for deleting tables based on cursor - sql

Question

I'm trying to build a dynamic function in Oracle using a cursor for all the tables that need to be dropped and re-created again. For example, I have the following example table structure:
CREATE TABLE All_tmp_DATA AS
(SELECT 'T_tmp_test1' As Table_NM, 'TEST1' As Process_name FROM DUAL UNION ALL
SELECT 'T_tmp_test2' As Table_NM, 'TEST1' As Process_name FROM DUAL UNION ALL
SELECT 'T_tmp_test3' As Table_NM, 'TEST1' As Process_name FROM DUAL)
The above tables starting with "T_tmp" represent all the tables in the database which needs to be dropped if their counts are >1 when starting the TEST1 process. I really need a function to pass in the parameter Process_name where I can input "TEST1", and build a loop using a cursor by binding it to the Table_NM from All_tmp_DATA and inserting it into table_name in the following code:
BEGIN
SELECT count(*)
INTO l_cnt
FROM user_tables
WHERE table_name = 'MY_TABLE';
IF l_cnt = 1 THEN
EXECUTE IMMEDIATE 'DROP TABLE my_table';
END IF;
END;

Answer 1

In the beginning, I'd suggest you not to use mixed case when naming Oracle objects.
Test case:
SQL> select * From all_tmp_data;
TABLE_NM PROCE
----------- -----
T_tmp_test1 TEST1
T_tmp_test2 TEST1
T_tmp_test3 TEST1
SQL> create table "T_tmp_test1" as select * From dept;
Table created.
SQL> -- I don't have "T_tmp_test2"
SQL> create table "T_tmp_test3" as select * From emp;
Table created.
SQL>
SQL> select table_name From user_Tables where upper(table_name) like 'T_TMP%';
TABLE_NAME
------------------------------
T_tmp_test3
T_tmp_test1
Procedure which drops tables contained in ALL_TMP_DATA:
as opposed to your code, I concatenated table name with DROP
as you use table names with mixed case, you have to enclose their names into double quotes, always (did I say not do use that?)
As the final select shows, those tables don't exist any more.
SQL> declare
2 l_cnt number;
3 begin
4 for cur_r in (select table_nm from all_tmp_data) loop
5 select count(*) into l_cnt
6 from user_tables
7 where table_name = cur_r.table_nm;
8
9 if l_cnt > 0 then
10 execute immediate ('drop table "' || cur_r.table_nm || '"');
11 end if;
12 end loop;
13 end;
14 /
PL/SQL procedure successfully completed.
SQL> select table_name From user_Tables where upper(table_name) like 'T_TMP%';
no rows selected
SQL>
As of the process column: I have no idea what is it used for so I did exactly that - didn't use it.

Answer 2

You can use the exception handling to handle such scenario directly as follows:
DECLARE
TABLE_DOES_NOT_EXIST EXCEPTION;
PRAGMA EXCEPTION_INIT ( TABLE_DOES_NOT_EXIST, -00942 );
BEGIN
FOR CUR_R IN (
SELECT TABLE_NM
FROM ALL_TMP_DATA
) LOOP
BEGIN
EXECUTE IMMEDIATE 'drop table "' || cur_r.table_nm || '"';
DBMS_OUTPUT.PUT_LINE('"' || cur_r.table_nm || '" table dropped.');
EXCEPTION
WHEN TABLE_DOES_NOT_EXIST THEN
DBMS_OUTPUT.PUT_LINE('"' || cur_r.table_nm || '" table does not exists');
END;
END LOOP;
END;
/