ORACLE : WITH Block statement

Query writing is fun but can be complex when we are referring multiple tables/views which has inlet/Joins /sub-query referred. on the best solution & organized way of writing such query in Oracle is using WITH Blocks.
Below I'm using simple example to help you get started with WITH-blocks
Tutorial : First block starts with "WITH" keyword  
WITH block_name AS ( ), Final statement includes Select statement with in query or join as needed treating each block as table. Below are 2 example showing with block usage.

Example : Consider 4 tables/views having needed information blinded with a connecting factor and say ID. Normal Query States :

        SELECT T1.Col1, T1.col2, T2.col3, T2.col4,
T2.col5 FROM Table1 T1 JOIN Table2 T2 ON Col6 = col7 
WHERE col6 IN ( SELECT TA.COLA FROM TableA TA JOIN TableB TB ON TA.COLA1 = tb.ColB1 ) 

Now to have more organized way to get this query executed using WITH Block  

CONDITION 01: Using blocks in WHERE clause

        WITH BLOCK1 AS (SELECT TA.COLA FROM
  TableA TA JOIN TableB TB ON TA.COLA1 = tb.ColB1), 
SELECT T1.Col1, T1.col2, T2.col3, T2.col4, T2.col5 FROM Table1 T1 JOIN Table2 T2 ON Col6 = col7 WHERE col6 IN 
( --Note:with block added as select statement & can be used at multiple places. 
SELECT block1.cola FROM BLOCK1 
) 

CONDITION 02: JOINING WITH blocks all together.
--Note : block starts from "WITH" statement

        WITH BLOCK1
AS
(SELECT TA.COLA FROM TableA TA JOIN
TableB TB ON TA.COLA1 = tb.ColB1 
), 
--Note: Except last with block all with block end with , 
BLOCK2 AS ( 
SELECT T1.Col1, T1.col2, T2.col3, T2.col4, T2.col5 FROM Table1
T1 JOIN Table2 T2 ON Col6 = col7 
) 
--final statement only includes Black name. 
SELECT * FROM Block2 B2, Block1 B1 WHERE B2.col6 = b1.COLA
  

Hope this help's you ----