MYSQL query using variable as table name in LEFT JOIN

SELECT var1,var开发者_运维百科2,var3,table_name 
FROM table1 LEFT JOIN table_name on var3=table_name.id

Meaning I want to dynamically left join table, depending on value of table_name from table1, since var3 is taken from there.

But the above query results in

table table_name does not exist

My mistake of mysql limitation?

Table names, as well as column names, can't be dynamic in an SQL query. So you have to apply your logic programmatically, using 2 queries, or with a stored procedure, see an example here: http://forums.mysql.com/read.php?98,126506,126598#msg-126598

Another way is to unite all tables with a union query:

SELECT *, 44 as table_origin FROM `Table_44`
UNION ALL
SELECT *, 58 as table_origin FROM `Table_58`;

You could even prepare that as view:

CREATE VIEW `AllTheTables` AS
SELECT *, 42 as table_origin FROM `Table_42`
UNION ALL
SELECT *, 44 as table_origin FROM `Table_44`
UNION ALL
SELECT *, 58 as table_origin FROM `Table_58`
UNION ALL
SELECT *, 69 as table_origin FROM `Table_69`;

And thus query it safely:

SELECT * FROM AllTheTables WHERE table_origin IN (44,58) AND something = 'foobar';
-- or --
SELECT * FROM AllTheTables WHERE table_origin = 42 AND something = 'the question';

In your exact case it could look like this:

SELECT var1, var2, var3, table_name 
FROM table1 LEFT JOIN AllTheTables ON table1.var3=AllTheTables.table_origin