Question

I have one table things full of items listed by ItemID. Given an ItemID, I need to get the record with the ItemID and all other items with the same name.

In the sample data below, given the ItemID of 1, I need to select all records with the same name (in this case, “poptarts”) as ItemID 1, including the record with ItemID 1.

ItemID = 1 name = poptarts
ItemID = 7 name = poptarts
ItemID = 8 name = cheddar
ItemID = 323 name = poptarts

select a.ItemID, a.name from things where a.ItemID = '1'
UNION
select b.ItemID, b.name from things where b.name = a.name

The SQL I’ve written above however does not pass a.name to the second select. Is there any way to pass the first name value to the second select? I would like for the statement to return itemid = 1 as the first row and 7 and 323 as the other rows.

Answer 1

UNION is only really used to concatenate two distinct sets. Based on your example, you could probably do something like this:

SELECT a.ItemID, a.Name
FROM things a
WHERE name IN (SELECT name FROM things WHERE itemID = 1)

There are lots of ways to write this kind of query and will depend on which flavor of SQL you’re using but this should be more or less universal.