sql - Can I modify below GroupBy clause into better one -


consider following cases

case 1:  tbl_a --------------- | cola | colb | ---------------      expected o/p:   1  0  |  1   |  0   | ---------------  case 2:  tbl_a --------------- | cola | colb | ---------------      expected o/p:   1  1 |  1   |  1   | ---------------  case 3:  tbl_a --------------- | cola | colb | ---------------     expected o/p:   1  1 |  1   |  0   | |  1   |  1   | ---------------  case 4:  tbl_a --------------- | cola | colb | ---------------     expected o/p:  null null | null | null | ---------------

the query simple, if there record cola = 1 , colb = 1 return it, if no such record exists return existing record cola = 1. have tried various ways. came groupby clause there simple way it.

if use cola = 1 , colb = 1 fails case 1 returns no rows.

 select cola, max(colb) group (cola)

is valid query? appreciated.

please try following. provides desired results posted cases.

select top 1 cola, colb    tbl_a   cola = 1 or cola null  order cola desc, colb desc;

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