Question

I have a load of code in place to ‘filter’ some records based on if a certain field appears in a list.

Currently SELCT * FROM table1 ... AND value IN (8, 6, 4, 2, 9, 1, 3, 5, 7) ...

With table1 structure :

CREATE TABLE IF NOT EXISTS `table1` (
    `uniqueid` varchar(32) NOT NULL,
    `value` int(11) DEFAULT NULL,
    ...
    PRIMARY KEY (`uniqueid`)
)

Now I have to store value in a separate table and there may well be more than one ‘value’ in the table.

New table1 structure:

CREATE TABLE IF NOT EXISTS `table1` (
    `uniqueid` varchar(32) NOT NULL,
    ...
    PRIMARY KEY (`uniqueid`)
)

New table2 structure

CREATE TABLE IF NOT EXISTS `table2` (
    `id` int(11) NOT NULL,
    `uniqueid` varchar(32) NOT NULL,
    `value` int(11) DEFAULT NULL,
    ...
    PRIMARY KEY (`id`)
)

You get the idea!

My question is how to check if any record in table2 for uniqueid is in the list given in the first example.

I considered using some sort of COUNT subquery but I’m not sure. I tried:

SELECT * FROM table1, table2 
            WHERE table1.uniqueid = table2.uniqueid 
            AND (SELECT COUNT(id) FROM table1, table2 
                       WHERE table2.uniqueid = table1.uniqueid ) > 0 
            AND table2.value IN (8, 6, ...

But it wasnt working and I don’t really like the approach, feels very messy.

Any help appreciated.

Answer 1

If you wanted to find those values that exist in 2 tables, implement an INNER JOIN.

   SELECT UniqueID
   FROM Table1 t1
   INNER JOIN Table2 t2 
     ON t1.UniqueID = t2.UniqueID
   WHERE (YourCritiera);