Imply bit with constant 1 or 0 in SQL Server

b1zrtrql  于 2023-02-18  发布在  SQL Server
关注(0)|答案(8)|浏览(155)

Is it possible to express 1 or 0 as a bit when used as a field value in a select statement?

e.g.

In this case statement (which is part of a select statement) ICourseBased is of type int.

case 
when FC.CourseId is not null then 1
else 0
end
as IsCoursedBased

To get it to be a bit type I have to cast both values.

case 
when FC.CourseId is not null then cast(1 as bit)
else cast(0 as bit)
end
as IsCoursedBased

Is there a short hand way of expressing the values as bit type without having to cast every time?

(I'm using MS SQL Server 2005)

pxq42qpu

pxq42qpu1#

cast (
  case
    when FC.CourseId is not null then 1 else 0
  end
as bit)

The CAST spec is "CAST (expression AS type)". The CASE is an expression in this context.

If you have multiple such expressions, I'd declare bit vars @true and @false and use them. Or use UDFs if you really wanted...

DECLARE @True bit, @False bit;
SELECT @True = 1, @False = 0;  --can be combined with declare in SQL 2008

SELECT
    case when FC.CourseId is not null then @True ELSE @False END AS ...
eoigrqb6

eoigrqb62#

You might add the second snippet as a field definition for ICourseBased in a view.

DECLARE VIEW MyView
AS
  SELECT
  case 
  when FC.CourseId is not null then cast(1 as bit)
  else cast(0 as bit)
  end
  as IsCoursedBased
  ...

SELECT ICourseBased FROM MyView
btxsgosb

btxsgosb3#

No, but you could cast the whole expression rather than the sub-components of that expression. Actually, that probably makes it less readable in this case.

fhity93d

fhity93d4#

Slightly more condensed than gbn's:

Assuming CourseId is non-zero

CAST (COALESCE(FC.CourseId, 0) AS Bit)

COALESCE is like an ISNULL() , but returns the first non-Null.

A Non-Zero CourseId will get type-cast to a 1, while a null CourseId will cause COALESCE to return the next value, 0

bkhjykvo

bkhjykvo5#

If you want the column is BIT and NOT NULL, you should put ISNULL before the CAST.

ISNULL(
   CAST (
      CASE
         WHEN FC.CourseId IS NOT NULL THEN 1 ELSE 0
      END
    AS BIT)
,0) AS IsCoursedBased
2ekbmq32

2ekbmq326#

The expression to use inside SELECT could be

CAST(IIF(FC.CourseId IS NOT NULL, 1, 0) AS BIT)
sqougxex

sqougxex7#

Unfortunately, no. You will have to cast each value individually.

7uhlpewt

7uhlpewt8#

Tested and functional

SELECT fc.CourseId, IsCoursedBased = CAST(CASE WHEN fc.CourseId IS NOT NULL THEN 1 ELSE 0 END AS BIT) 
FROM fc

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