With clause join using ISO JOIN Sysntax

Question

Hi,
One of my query looks like:
SELECT t2.col1,
              t3.col1,
              t3.col2
FROM t2
JOIN t2 ON t2.col1 = t3.col1;
Now I need to use a WITH clause to hold some values which has to be used to filter the results from the original query. Something like:
with t1 AS (Select col1
                   FROM tab1)
SELECT t2.col1,
              t3.col1,
              t3.col2
FROM t2
JOIN t3 ON t2.col1 = t3.col1
WHERE t2.col2 = t1.col1;
But the problem is I have to use t1 in the FROM clause before I can use it in the WHERE clause. My question is how do I use t1 in Where clause without joining with t2 & t3?

Answer 1

Hi,
Whenever you have a problem, please post a little sample data (CREATE TABLE and INSERT statements, relevant columns only) from all tables involved, so that the people who want to help you can re-create the problem and test their ideas.
Also post the results you want from that data, and an explanation of how you get those results from that data, with specific examples.
Always say which version of Oracle you're using (for example, 11.2.0.2.0).
See the forum FAQ: https://forums.oracle.com/message/9362002
Do you really need to use a WITH clause?  It's hard to tell what you want to do just by looking at some code that doesn't do it, but it looks like you're trying to do this:
SELECT  t2.col1,
        t3.col1,
        t3.col2
FROM    t2
JOIN    t3  ON t2.col1 = t3.col1
WHERE   t2.col2 IN (
                       SELECT  col1
                       FROM    tab1
If you really did need a WITH clause, you could reference it like this
with t1 AS
    Select col1
    FROM   tab1
SELECT  t2.col1,
        t3.col1,
        t3.col2
FROM    t2
JOIN    t3  ON t2.col1 = t3.col1
WHERE   t2.col2 IN (
                       SELECT  col1
                       FROM    t1
Joining t1, like Alberto suggested, is another possibility, but be careful: if t1.col1 is not unique, you may get duplicate rows.