Truncating a table in a stored procedure

Question

When I run the following in an Oracle shell it works fine

truncate table table_name

But when I try to put it in a stored procedure

CREATE OR REPLACE PROCEDURE test IS
BEGIN
    truncate table table_name;
END test;
/

it fails with

ERROR line 3, col 14, ending_line 3, ending_col 18, Found 'table', Expecting:  @   ROW  or   (   or   .   or   ;   :=

Why?

Answer 1

All DDL statements in Oracle PL/SQL should use Execute Immediate before the statement. Hence you should use:

execute immediate 'truncate table schema.tablename';

Answer 2

As well as execute immediate you can also use

DBMS_UTILITY.EXEC_DDL_STATEMENT('TRUNCATE TABLE tablename;');

The statement fails because the stored proc is executing DDL and some instances of DDL could invalidate the stored proc. By using the execute immediate or exec_ddl approaches the DDL is implemented through unparsed code.

When doing this you neeed to look out for the fact that DDL issues an implicit commit both before and after execution.

Answer 3

try the below code

execute immediate 'truncate table tablename' ;

Answer 4

You should know that it is not possible to directly run a DDL statement like you do for DML from a PL/SQL block because PL/SQL does not support late binding directly it only support compile time binding which is fine for DML. hence to overcome this type of problem oracle has provided a dynamic SQL approach which can be used to execute the DDL statements.The dynamic sql approach is about parsing and binding of sql string at the runtime. Also you should rememder that DDL statements are by default auto commit hence you should be careful about any of the DDL statement using the dynamic SQL approach incase if you have some DML (which needs to be commited explicitly using TCL) before executing the DDL in the stored proc/function.

You can use any of the following dynamic sql approach to execute a DDL statement from a pl/sql block.

1) Execute immediate

2) DBMS_SQL package

3) DBMS_UTILITY.EXEC_DDL_STATEMENT (parse_string IN VARCHAR2);

Hope this answers your question with explanation.