I'm trying to create a procedure for deleting rows how many rows inputted in special table, but I can't use table in input parameters - sql

Question

CREATE OR REPLACE PROCEDURE delete_rows (table_name IN USER_TABLES.table_name%type, row_count in number)
IS
BEGIN
execute immediate 'delete from'||table_name||' where rowid in (select rowid from table_name fetch first Row_count rows only)';
dbms_output.put_line(sql%rowcount);
END;
/
I get this error:
PLS-00357: Table View Or Sequence reference 'EMPLOYEES' not allowed in this context

Answer 1

When working with dynamic SQL, it is almost ALWAYS useful to prepare statement you'll execute, review it and - once you're satisfied with it - actually execute it. Here's what your code is trying to do:
SQL> set serveroutput on
SQL> CREATE OR REPLACE PROCEDURE delete_rows
2 (table_name IN USER_TABLES.table_name%type,
3 row_count in number)
4 IS
5 l_str varchar2(200);
6 BEGIN
7 l_str := 'delete from'||table_name||' where rowid in ' ||
8 '(select rowid from table_name fetch first Row_count rows only)';
9 dbms_output.put_line(l_str);
10 -- execute immediate l_str;
11 dbms_output.put_line(sql%rowcount);
12 END;
13 /
Procedure created.
SQL> exec delete_rows('test', 2);
delete fromtest where rowid in (select rowid from table_name fetch first
Row_count rows only)
PL/SQL procedure successfully completed.
SQL>
What do you think, can you really run it? Sure you can, but it'll fail:
SQL> delete fromtest where rowid in (select rowid from table_name fetch first
2 Row_count rows only)
3 /
delete fromtest where rowid in (select rowid from table_name fetch first
*
ERROR at line 1:
ORA-00942: table or view does not exist
SQL>
Let's fix it. It is a good habit to precede parameters' names with a prefix so that you'd easily recognize them in the code; it also helps in where clause because - if you name the parameter the same as column, you'll get wrong result.
Also
, if you're worried about SQL injection, you could include call(s) to the `DBMS_ASSERT` package:
SQL> CREATE OR REPLACE PROCEDURE delete_rows
2 (par_table_name IN USER_TABLES.table_name%type,
3 par_row_count in number)
4 IS
5 l_str varchar2(200);
6 l_table_name user_tables.table_name%type;
7 BEGIN
8 l_table_name := dbms_assert.sql_object_name(par_table_name);
9
10 l_str := 'delete from ' || l_table_name ||' where rowid in ' ||
11 '(select rowid from ' || l_table_name ||
12 ' fetch first ' || par_row_count || ' rows only)';
13 dbms_output.put_line(l_str);
14 -- execute immediate l_str;
15 dbms_output.put_line(sql%rowcount);
16 END;
17 /
Procedure created.
OK; what's the new result:
SQL> exec delete_rows('test', 2);
delete from test where rowid in (select rowid from test fetch first 2 rows only)
PL/SQL procedure successfully completed.
Does this work? Yes, it does:
SQL> delete from test where rowid in (select rowid from test fetch first 2 rows only);
2 rows deleted.
SQL> rollback;
Rollback complete.
SQL>
OK; the final fix of the procedure: include execute immediate:
SQL> CREATE OR REPLACE PROCEDURE delete_rows
2 (par_table_name IN USER_TABLES.table_name%type,
3 par_row_count in number)
4 IS
5 l_str varchar2(200);
6 l_table_name user_tables.table_name%type;
7 BEGIN
8 l_table_name := dbms_assert.sql_object_name(par_table_name);
9
10 l_str := 'delete from ' || l_table_name ||' where rowid in ' ||
11 '(select rowid from ' || l_table_name ||
12 ' fetch first ' || par_row_count || ' rows only)';
13 -- dbms_output.put_line(l_str);
14 execute immediate l_str;
15 dbms_output.put_line('Deleted ' || sql%rowcount || ' row(s)');
16 END;
17 /
Procedure created.
SQL> exec delete_rows('test', 2);
Deleted 2 row(s)
PL/SQL procedure successfully completed.
SQL>

Answer 2

There are 2 mistakes.
You are missing a space after from.
row_count must be passed as parameter.
create or replace procedure delete_rows (table_name IN USER_TABLES.table_name%type, row_count in number)
IS
BEGIN
execute immediate 'delete from '||table_name||' where rowid in (select rowid from ' ||table_name||' fetch first '|| Row_count || ' rows only)';
dbms_output.put_line(sql%rowcount);
END;
/