SQL Queries: Queries depending on previous queries and merging results

Following problem:

Query 2 and Query 3 depend on the results of Query 1 and Query 4 depends on the results of query 2. How would you express these queries without executing the same query multiple times?

Example:

Query 1

SELECT id, color, part FROM T1

Query 2

SELECT id, owner FROM T2 WHERE T2.color in (SELECT id, color, part FROM T1)

Query 3

SELECT id from T3 开发者_如何学编程where T3.part in (SELECT id, color, part FROM T1)

Query 4

SELECT id from T4 where T4.owner in (SELECT id, owner FROM T2 WHERE T2.color in (SELECT id, color, part FROM T1))

edit

At the end i need the union of the result

Query1 union Query2 union Query3 union Query4

Now as you can see, I have copied and pasted the previous queries, there must be a better way of doing this.

Just join them by the specific columns.

select * from T1  
inner join T2  on T1.color=T2.color 
inner join T3 on T3.part=T1.part 
inner join T4 on T4.owner=T2.owner

Do you really need four different result sets? How many rows are you expecting in each set and what kind of entities are T1, T2, T3, T4 - because it may be possible to combine those queries into a single set.

In addition, this:

SELECT id, owner FROM T2 WHERE T2.color in (SELECT id, color, part FROM T1)

isn't valid SQL, you probably mean:

SELECT id, owner FROM T2 WHERE T2.color in (SELECT color FROM T1)