Select using dynamically generated tablename

Question

I\'ve got the following problem. My table (geo_table) structure is as follows:

foreign_table_id | foreign_table_name | some_other_fields...


        

Answer 1

If you know all possible table names then you can implement it using conditional syntax:

SELECT foreign_table_id, foreign_table_name FROM `geo_table` gt
WHERE 
    CASE gt.foreign_table_name
        WHEN 'table1' THEN 
            EXISTS (
                SELECT * FROM table1
                WHERE id = gt.foreign_table_id
            )
        WHEN 'table2' THEN 
            EXISTS (
                SELECT * FROM table2
                WHERE id = gt.foreign_table_id
            )
        ELSE
            FALSE
    END

Answer 2

This should be done dynamically :

declare @tablename varchar(50)
set @tablename = 'test'
declare @sql varchar(500)
set @sql = 'select * from ' + @tablename
exec @sql