Joining Tables at a time only one column should Come as Output in a Single Query

Question

Hi

i have joined around 7 tables, based on conditions at a time only one column should exist in a SINGLE QUERY, suppose

For Example :-

i have a columns of A,B,C,D,E,F,G,H in a table after JOINING some tables, i want 'F' column to be insert some value based on requirement, that Time 'G' Column is not required n should not be their.

sometimes i want 'G' column, that time 'F' Column is not required n should be not their, This should be achieved using SINGLE QUERY. 

how to achieve This type of Scenarios ??????????

Thanks

Supreeth

Answer 1

You can use CASE for this....Use the CASE with the corresponding expression and return the corresponding column for every expression within the case..

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Murali Krishnan

Answer 2

Hi Supreeth,

Say if u have Query is Select A,B,C,D,E,F,G From table Where <Conditions>,so What u can do is make an Inline query something like

Select A,B,C..,Case When <Condition> Then G When <Condition> Then F End From (Select A,B,C,D,E,F,G From Table where <Filter conditions> ) As SubTable. This may help u out with ur requirement.

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Please have look on the comment

Answer 3

Santhosh ,

That A,B,C,D,E,F,G,H columns are output After Joining Several Tables, In place of Coming output like that, i want the output lik this A,B,C,D,E,F(when 'F' Requirement), sometimes i want output like this A,B,C,D,E,G(When 'G' Requirement)

select A,B,C,D,E,F,G,H

from <Table>

Inner Jioin <Table>

On<Condition>

Inner Join

On

etc.,

Answer 4

Supreeth we need sample data to help you better...

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Murali Krishnan

Answer 5

Supreeth,

Though u r fetching the results  lik this A,B,C,D,E,F(when 'F' Requirement), sometimes i want output like this A,B,C,D,E,G(When 'G' Requirement), so at a time u need either of one column value based on requirement right. so why don't u try fetching the column by using case statement.

If this is really not helping u out just give a model data so that we can wrk it on it and then try to find a proper solution.

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Please have look on the comment

Answer 6

 Murali and Santhosh

i have to join from several tables in that one table say 'Test' contains

columns 'file_Key' and 'Table_Key' based on filename say 'ABC.txt' that file _key is generated. and based on table_name say 'Emp' table_key is generated
when i select those columns File_key and Table_Key. if that 'Test' table contains both file_key and Table_key then
it should select both columns , if that 'Test' table contains only File Information, then it should display only 'File_key',same ike if that 'Test' table contains Table Information, then it should display Table_key as a output.

Answer 7

I have done it Using Coalesce Function.