MySql Query Optimisation

Question

I have 3 tables, I need advice on how to get data from them.

Table name

details_varchar  

details_int  

details_date

each of them have value_id[Int] and value_name [value_name type varies as per table name - Varchar, Int, Date]

Conditions

• only one unique value_id will be present in any one of the 3 tables. i.e ID from 1 to n are stored in these tables according to their Data Types. If value_id = 1 and value_name[type] = int then it stores in details_int table.

What I need

select value_name from 3 tables[may appear in any one of the table] where value_id = '[I have this value stored in a variable]'

What I tried

UNION - but all the table needs to have same column type.

JOINS - All the fields should be connected.[I guess]

Answer 1

SELECT value_name
FROM (  SELECT value_name
        FROM details_varchar
        WHERE value_id = {$int_value_id}
        UNION ALL
        SELECT value_name
        FROM details_int
        WHERE value_id = {$int_value_id}
        UNION ALL
        SELECT value_name
        FROM details_date
        WHERE value_id = {$int_value_id}) AS h

This should give you what you want?