Select column, if blank select from another

How does one detect whether a开发者_开发知识库 field is blank (not null) and then select another field if it is?

What I really need is a IsBlank function that works the same as IsNull but with with blanks.

REPLACE doesn't work with blanks, COALESCE only works with NULLS.

How about combining COALESCE and NULLIF.

SELECT COALESCE(NULLIF(SomeColumn,''), ReplacementColumn)
FROM SomeTable

You can use a CASE statement for this

select 
Case WHEN Column1 = '' OR Column1 IS NULL OR LEN (TRIM (Column1))  = 0 
     THEN Column2 
     ELSE Column1 END as ColumnName
from TableName

EDIT: You can't use IF() in mssql.

Use an IF statement in the SELECT portion of your SQL:

SELECT IF(field1 != '', field1, field2) AS myfield FROM ...

You could always write an isBlank() function, something like

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE FUNCTION isBlank
(
    @CheckExpression varchar, @ReplacementExpression varchar
)
RETURNS varchar
AS
BEGIN
    IF @CheckExpression IS NOT NULL
    BEGIN
        IF @CheckExpression='' or LEN(@CheckExpression) = 0
        RETURN @ReplacementExpression
    ELSE
        RETURN @CheckExpression
    END

    RETURN @ReplacementExpression
END
GO