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by nickpeterson 3703 days ago
I don't know if postgres allows one to treat boolean as 0 and 1 natively but in t-sql, the equivalent would be something like:

  DECLARE @orders TABLE (
      category VARCHAR(5),
      express_delivered INT 
  );
  
  INSERT INTO @orders (category, express_delivered) VALUES ( 'food', 1);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'food', 0);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'shoes',0);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'shoes',0);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'auto', 1);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'auto', 1);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'book', 1);
  INSERT INTO @orders (category, express_delivered) VALUES ( 'book', 0);
  
  SELECT 
      category, 
      CASE WHEN SUM(express_delivered) = 0 THEN 0 ELSE 1 END AS ever_been_express_delivered
  FROM @orders
  GROUP BY category
4 comments
Pxtl 3703 days ago
Goddamnit I hate how there is no true boolean datatype in t-sql. I can't write a simple predicate without comparing its output to 1 or 0.
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gary__ 3703 days ago
Since SQL Server 2012, you can use the lovely IIF statement, which is translated into a CASE behind the scenes.

So:

CASE WHEN SUM(express_delivered) = 0 THEN 0 ELSE 1 END AS ever_been_express_delivered

becomes:

IIF(SUM(express_delivered) = 0, 0, 1) AS ever_been_express_delivered

https://msdn.microsoft.com/en-GB/library/hh213574.aspx

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aetherson 3703 days ago
That's fine for an "or" aggregation, but it's harder for an "and" aggregation, in which case I guess you'd have to say:

select category case when sum(express_delivered) = count(express_delivered) then 1 else 0 end as always_been_express_delivered from etc.

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MSM 3703 days ago
I think instead of trying to shoehorn the "AND" that he discusses in the article into a case statement you'd just look for each category to see if there has been a non expressed delivered package.

  SELECT 
      category, 
      ISNULL(NonExpress.NonExpress, 0) AS ever_been_non_express_delivered
  FROM @orders O
  OUTER APPLY (
     SELECT TOP 1 1 as [NonExpress]
     FROM @Orders O2
     WHERE O2.Category = O.Category
        AND express_delivered = 0
  ) NonExpress
  GROUP BY category
Edit: Changed the logic up, the original code's field was contradicting my logic.
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nickpeterson 3703 days ago
How about:

  CASE WHEN MIN(express_delivered) = 0 THEN 0 ELSE 1 END AS always_been_express_delivered
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netcraft 3703 days ago
its one of my few aggravations with pgsql, but you cant use 0 and 1 unless they are quoted. The only non-quoted values you can use are TRUE and FALSE. http://www.postgresql.org/docs/9.1/static/datatype-boolean.h...
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