Selecting not null column

I have a table with varbinary(max) column and nvarchar(max) column. One of them is null and the other has a value.

I would like to return the column that has the value as a varbinary(max) c开发者_开发百科olumn. So far I have tried this, that does not work:

SELECT 
      A =  
      CASE A
         WHEN NULL THEN B
         ELSE A 
      END
FROM Table

---

SELECT COALESCE(A, CAST(B As varbinary(max)))

UPDATE: In response to comments (thanks) and assuming B is the nvarchar(max) column, I have moved the CAST inside the COALESCE

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Try SELECT ISNULL(A, cast(B AS varbinary(max))) FROM TABLE

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Your case statement evaluates to the dreaded A = NULL:

CASE A WHEN NULL THEN B ELSE A END

Is the same as:

CASE WHEN A = NULL then B ELSE A END

One way to fix this is to use A IS NULL, like:

CASE WHEN A IS NULL THEN B ELSE A END

Or even simpler:

COALESCE(A,B)

Both the when and the coalesce will assume the data type of the first argument. To cast the result to varbinary, you can place the varbinary column first, or explicitly cast:

COALESCE(CAST(A AS VARBINARY(MAX)),B)

---

here is the full code of create table and insert value and apply my code and only retrieve not null value

CREATE TABLE [dbo].[SUPPLIER](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [SUPPLIER_NAME] [varchar](100) NOT NULL,
    [ADDRESS] [varchar](150) NULL,
    [CREATE_DATE] [datetime] NULL,)

    INSERT INTO [MyPayrol].[dbo].[SUPPLIER]
           ([SUPPLIER_NAME]           
           ,[CREATE_DATE])
     VALUES
           ('Khaled Nabil'
           ,GETDATE())


declare @inumberofcolumn int

select @inumberofcolumn= count(*) 
from sys.columns where OBJECT_NAME(object_id) = 'supplier'

declare @nameofcolumn varchar(100)

set @nameofcolumn =''

declare @counter int

set @counter=1


declare @colname varchar(100)

declare @statment varchar(100)

declare @value varchar(100)

while @counter <=@inumberofcolumn
begin

    select @colname= COL_NAME(object_id('[dbo].[SUPPLIER]'),@counter)
    declare @data table ([value] varchar(100))

    --set @statment = 'select '+@colname+' from [dbo].[SUPPLIER]'
      insert @data exec ('SELECT top 1 '+ @colname +' from [dbo].[SUPPLIER]') 
      select @value = [value] from @data
    if @value is not  null
    begin
        if @counter = 1
        begin   
            set @nameofcolumn = @nameofcolumn + @colname
        end
        else
        begin
            set @nameofcolumn = @nameofcolumn + ','+ @colname
        end
    end
    set  @counter = @counter+1
end



execute ('select '+@nameofcolumn+' from [dbo].[SUPPLIER]')