When exists - Dev Shed

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October 31st, 2012, 10:57 AM

DaanOoms

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Join Date: Oct 2012

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When exists

I have the following data:

A B
1 1
2 2
2 .
3 .

I want a third row that gives the value 1 when A does not exists in the whole column B:

A B output
1 1 0
2 2 0
2 . 0 (because the value of ID1 does exist in ID2)
3 . 1 (because the value of ID1 doesn't exist in ID2)

Last edited by DaanOoms : October 31st, 2012 at 11:00 AM. Reason: Unclear representation

October 31st, 2012, 11:44 AM

cafelatte

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Code:

SELECT x.*
     , y.b IS NULL output 
  FROM my_table x 
  LEFT 
  JOIN my_table y 
    ON y.b = x.a;

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