Conditional myslq query

I’m wondering how to set a query to look for something in one table, and if it exists (or doesn’t exist) insert a row into another, otherwise do nothing. This is what I’ve got so far, which works for what I need it to do, but I need some kind of restriction on when this query is run:

INSERT IGNORE INTO jos_juga_u2g (user_id, group_id)
VALUES ({userid}, 4)

Basically, I need to look into a table which stores order info, and if a certain item_id exists, then run the query. Otherwise, do nothing.

Try (didn’t test it, and you have to add the correct name of the order table (I assumed the user_id is present in the order table))

INSERT IGNORE INTO jos_juga_u2g (user_id, group_id)

  , 4
FROM jos_whatever_the_order_table_is_called AS o
INNER JOIN jos_tienda_orderitems AS oi
ON oi.order_id = o.order_id
AND oi.product_id = 28
WHERE o.user_id = {userid}

Would that be the equivalent of an IF statement? IF a certain value exists in table A, insert a row into table B. IF the value does not exist, do nothing?

That would insert a row in table B for each row found in table A.

Why don’t you give a more detailed description of what you want? If you find what in table A, what do you want to insert in table B?

This is the query i’m trying to put together but since I’m weak with sql, I can’t make it work. This probably isn’t even the right syntax. I’m trying to put a user into a certain usergroup if a certain product is purchased.

SELECT product_id, order_id FROM jos_tienda_orderitems
IF (product_id=28)
INSERT IGNORE INTO jos_juga_u2g (user_id, group_id)
VALUES ({userid}, 4)

I didn’t understand much from your explanation, but maybe you want to use

INSERT INTO tablename

FROM tablename