Understanding simple stored procedure: Moving output to a variable

I'm hoping I can get some help with understanding a simple stored procedure. Basically, I want to store the output of a select statement in a variable and then print out the value of the variable.

I found a very similar question here: Simple Stored Procedure Question

And the code looks as follows:

CREATE PROCEDURE ReturnPrice 
   @carID int,
   @price decimal(18,2) output 
AS 
   SELECT 
      @price = Price 
   FROM 
      dbo.Cars 
   WHERE 
      CarID = @carID 

My question is this: How do I get the value of @carID?

If I try this:

declare @carOutput varchar(50)
exec carInformation, '@carOutput varchar(50) output', 开发者_Go百科 @carOutput output

I get an error of:

Msg 170, Level 15, State 1, Line 3
Line 3: Incorrect syntax near ','.

Thank you!

exec carInformation, '@carOutput varchar(50) output',  @carOutput output
                   ^bad

exec carInformation  '@carOutput varchar(50) output',  @carOutput output
                   ^good

but also '@carOutput varchar(50) output' must be an int, but you are passing in a string

you need to have the calling application already know the value for @carID, and the procedure uses that value to return the price.

so try something like:

DECLARE @CarID_x int
       ,@Price_x decimal(18,2)

SET @CarID_x=123

EXEC ReturnPrice @CarID, @Price_x OUTPUT 
PRINT @Price_x

or

DECLARE @Price_x decimal(18,2)

EXEC ReturnPrice 123, @Price_x OUTPUT 
PRINT @Price_x

both code examples above will return the Price column value for the dbo.Cars row that has the CarID value of 123.

If you don't know the CarID then run:

SELECT 
      CarID, Price 
   FROM dbo.Cars 

and you will get a result set containing all the prices for all the cars.