How To have Dynamic SQL in MySQL Stored Procedure

Question

How do you build and use dynamic sql in a MySQL stored procedure?

Answer 1

I don't believe MySQL supports dynamic sql. You can do "prepared" statements which is similar, but different.

Here is an example:

mysql> PREPARE stmt FROM 
    -> 'select count(*) 
    -> from information_schema.schemata 
    -> where schema_name = ? or schema_name = ?'
;
Query OK, 0 rows affected (0.00 sec)
Statement prepared
mysql> EXECUTE stmt 
    -> USING @schema1,@schema2
+----------+
| count(*) |
+----------+
|        2 |
+----------+
1 row in set (0.00 sec)
mysql> DEALLOCATE PREPARE stmt;

The prepared statements are often used to see an execution plan for a given query. Since they are executed with the execute command and the sql can be assigned to a variable you can approximate the some of the same behavior as dynamic sql.

Here is a good link about this:

Don't forget to deallocate the stmt using the last line!

Good Luck!