MySQL在单个查询中具有不同位置的多重选择

Question

First of, at the moment I am forced to use MySQL despite it being deprecated. I am very well aware of that fact. Hopefully you guys can still help me with my sql syntax.

I am trying to access several columns from some different tables. Problem is, some of the columns require a different where clause than the last column I need, and the where clause for the last column requires info from the rest of the query so I cannot split it up into multiple queries, I've tried.

I cannot use union because one select statement selects four columns, and the other one selects one column.

Query:

(SELECT DISTINCT inventory.Quantity, itemtypes.Itemtypename, 
itemtypes.ItemtypeID, inventory.ItemID
FROM inventory JOIN itemtypes ON inventory.ItemtypeID = itemtypes.ItemtypeID
JOIN sets ON inventory.SetID = sets.SetID
WHERE inventory.ItemtypeID = itemtypes.ItemtypeID
AND itemtypes.Itemtypename = 'Set'
AND sets.SetID = '".$setid."')
UNION
(SELECT DISTINCT sets.Setname
FROM sets JOIN inventory ON sets.SetID = inventory.ItemID
WHERE sets.SetID = inventory.ItemID)

This is what I tried to use, with no success. I cannot seem to find any other way of linking to different select statements without using multiple queries (with due to the structure of my PHP file, is impossible to do properly). The rest of the file will work, if only this problem gets solved. Hopefully you guys can help me with this, please let me know if this is even possible to do. Let me know if you need to see my PHP code as well. $setid is derived from a get in the file and contains a value existing in the database.

Answer 1

May be, you can try like this. It works fine in SQL Server.

SELECT TMP1.Quantity,TMP1.Itemtypename, TMP1.ItemtypeID, TMP1.ItemID, TMP2.Setname
FROM(
SELECT DISTINCT 
inventory.Quantity, 
itemtypes.Itemtypename, 
itemtypes.ItemtypeID, 
inventory.ItemID
FROM inventory 
JOIN itemtypes ON inventory.ItemtypeID = itemtypes.ItemtypeID
JOIN sets ON inventory.SetID = sets.SetID
WHERE inventory.ItemtypeID = itemtypes.ItemtypeID
AND itemtypes.Itemtypename = 'Set'
AND sets.SetID = '".$setid."'
) AS TMP1,
(
SELECT DISTINCT 
sets.Setname
FROM sets 
JOIN inventory ON sets.SetID = inventory.ItemID
WHERE sets.SetID = inventory.ItemID
) AS TMP2

Hope this is what you want. Your question seems very ambiguous.