how to select the unique column names from 4 tables using the given query

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SQL

select *
from t1
where exists(select * from t2 where t2.col1 = t1.col1 and t2.col2 = t1.col2)

how to modify same query for four tables

Please give me a Help

Posted 25-May-12 23:05pm

mansoorttg

Updated 25-May-12 23:22pm

P.Salini

v2

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db7uk 26-May-12 9:32am

Could you not use a union statement?

Sandeep Mewara 27-May-12 11:18am

You talking of joining table and having all in a result set or getting a list of columns via query? What does unique mean?

2 solutions

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Wendelius · Answer 1 · 2012-05-26T10:31:00

Solution 1

If your question is about the tables having same column names and you want to rename them in the result set, then you should define aliases for them. Something like:

SQL

SELECT t1.Col1 AS T1_col1,
       t1.Col2 AS T1_col2,
       t2.Col1 AS T2_col1,
       t2.Col2 AS T2_col2,
       ...
FROM  Table1 t1 INNER JOIN Table2 t2 ON t1.PrimaryKeyCol =  t2.ForeignKeyCol
      ...
WHERE ...

Posted 26-May-12 10:31am

Wendelius

Comments

Maciej Los 29-May-12 4:55am

+5!

Wendelius 1-Jun-12 0:46am

Thanks :)

Prosan · Answer 2 · 2012-06-01T00:58:00

if you want unique name than you could not use select * instead of use tablename.fieldName as newname

SQL

select t1.FName as f1,
t2.FName as f2,
t3.FName as f3,
t4.FName as f4

from t1 inner join t2 on t1.col=t2.col 
inner join t3 on  t2.col=t3.col 
inner join t4 on  t3.col=t4.col 
where ...