Question

My question relates to identifying which table and schema a mysql command is executed on. I’m running this from a PDO wrapper in PHP

For example:

USE db1;
SELECT * FROM `table`;

I can get the name of the table from using DESCRIBE SELECT * FROM table and assume that the name of the schema is db1.

Now, when i want to do something like this

USE db1;
SELECT * FROM `db2`.`table`

I can get the name of the table using the describe command again. However i can not find a method in MySQL that gives me the schema on which the command was executed.

Is there a way to extract a database and table name from a MySQL command using regex. Assuming there is no join and the command is only a SELECT

Answer 1

Using the query the query analyzer produces should give you what you want I think. To be clear this is table test in database test.

explain extended select * from test;

+----+-------------+-------+------+---------------+------+---------+------+------+----------+-------+
| id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra |
+----+-------------+-------+------+---------------+------+---------+------+------+----------+-------+
|  1 | SIMPLE      | test  | ALL  | NULL          | NULL | NULL    | NULL |    5 |   100.00 |       |
+----+-------------+-------+------+---------------+------+---------+------+------+---------    -+-------+
1 row in set, 1 warning (0.00 sec)

Dont forget to do the show warnings

show warnings;
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------+
| Level | Code | Message                                                                                                                              |
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------+
| Note  | 1003 | select `test`.`test`.`id` AS `id`,`test`.`test`.`name` AS `name`,`test`.`test`.`date_modified` AS `date_modified` from `test`.`test` |
+-------+------+---------------------------------------------------------------------------    -----------------------------------------------------------+
1 row in set (0.00 sec)