How to use Switch in SQL Server

问题

I want to use CASE in my stored procedure. I am getting some syntax error in my code:

select 
   case @Temp
   when 1 then (@selectoneCount=@selectoneCount+1)
   when 2 then (@selectoneCount=@selectoneCount+1)
   end

When running, I'm getting:

incorrect syntax near '='.

at this line here:

@selectoneCount = @selectoneCount + 1

near the equal.

Actually I am getting return value from a another sp into @temp and then if @temp =1 then I want to increment the count of @SelectoneCount by 1 and so on. Please let me know what is the correct syntax.

回答1:

The CASE is just a "switch" to return a value - not to execute a whole code block.

You need to change your code to something like this:

SELECT 
   @selectoneCount = CASE @Temp
                         WHEN 1 THEN @selectoneCount + 1
                         WHEN 2 THEN @selectoneCount + 1
                     END

If @temp is set to none of those values (1 or 2), then you'll get back a NULL

回答2:

This is a select statement, so each branch of the case must return something. If you want to perform actions, just use an if.

回答3:

    select 
       @selectoneCount = case @Temp
       when 1 then (@selectoneCount+1)
       when 2 then (@selectoneCount+1)
       end

   select  @selectoneCount 

回答4:

Actually i am getting return value from a another sp into @temp and then it @temp =1 then i want to inc the count of @SelectoneCount by 1 and so on. Please let me know what is the correct syntax.

What's wrong with:

IF @Temp = 1 --Or @Temp = 2 also?
BEGIN
    SET @SelectoneCount = @SelectoneCount + 1
END

(Although this does reek of being procedural code - not usually the best way to use SQL)

来源：https://stackoverflow.com/questions/11220226/how-to-use-switch-in-sql-server