Prepared Statements Mysql - mysql

Question

I have a prepared statement I want to execute direct to the MySQL server;
USE `testdb`;
SET #t = (
SELECT GROUP_CONCAT(mytab.TABLE_NAME SEPARATOR ', ')
FROM (SELECT * FROM information_schema.TABLES as `m` WHERE table_schema = 'testdb' AND table_name LIKE 'mi_%' LIMIT 0,1) as `mytab`
);
PREPARE `stmt1` FROM 'DROP TABLE t';
EXECUTE `stmt1` USING #t;
DEALLOCATE PREPARE `stmt1`;
However, when I execute it returns an error on the EXECUTE line saying
Error Code: 1210. Incorrect arguments to EXECUTE
I would appreciate any help on what I'm doing wrong.
I have mysql version 5.1.68

Answer 1

Your issue can be resolved with preparing fully static DDL before executing. Sample:
Tables:
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| a |
| b |
+----------------+
2 rows in set (0.00 sec)
And your (little modified) SQL:
mysql> SET #t = (SELECT GROUP_CONCAT(mytab.TABLE_NAME SEPARATOR ', ') FROM (SELECT * FROM information_schema.TABLES as `m` WHERE table_schema = 'test'
AND table_name LIKE 'a%' LIMIT 0,1) as `mytab`);
Query OK, 0 rows affected (0.06 sec)
mysql> select #t;
+------+
| #t |
+------+
| a |
+------+
1 row in set (0.00 sec)
Now, DDL:
mysql> set #drop = CONCAT('DROP TABLE ', #t);
Query OK, 0 rows affected (0.00 sec)
mysql> select #drop;
+--------------+
| #drop |
+--------------+
| DROP TABLE a |
+--------------+
1 row in set (0.00 sec)
And, finally, prepared statement:
mysql> PREPARE `stmt1` FROM #drop;
Query OK, 0 rows affected (0.00 sec)
Statement prepared
mysql> EXECUTE `stmt1`;
Query OK, 0 rows affected (0.00 sec)
You'll get:
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| b |
+----------------+
1 row in set (0.00 sec)
You can use only one variable (I've added #drop to increase readability)