sql - In MySQL: How to pass a table name as stored procedure and/or function argument?

Question

For instance, this does not work:

DELIMITER //
CREATE PROCEDURE countRows(tbl_name VARCHAR(40))
  BEGIN
    SELECT COUNT(*) as ct FROM tbl_name;
  END //

DELIMITER ;
CALL countRows('my_table_name');

Produces:

ERROR 1146 (42S02): Table 'test.tbl_name' doesn't exist

However, this works as expected:

SELECT COUNT(*) as ct FROM my_table_name;

What syntax is required to use an argument as a table name in a select statement? Is this even possible?

Answer 1

Prepared statements are what you need.

CREATE  PROCEDURE `test1`(IN tab_name VARCHAR(40) )
BEGIN
 SET @t1 =CONCAT('SELECT * FROM ',tab_name );
 PREPARE stmt3 FROM @t1;
 EXECUTE stmt3;
 DEALLOCATE PREPARE stmt3;
END $$