T-SQL：WHERE子句-如何根据输入变量进行调整

Question

Using SQL Server 2008. I have an input param in my stored proc called '@State'. The param can basically be '--All--' or can contain the state to filter.

So, if it is '--All--' I don't want to incorporate the @State into the where clause. Otherwise I'd like it to filter based on the provided @State. So basically it could result in this....

SELECT * FROM MyTable
WHERE Type='AAA' AND Status=@Status

or, if they pass '--All--'

SELECT * FROM MyTable
WHERE Type='AAA'

How can I do this in a stored proc?

Answer 1

SELECT
    *
FROM
    MyTable
WHERE
    Type='AAA'
    AND Status = CASE @Status WHEN '--All--' THEN Status ELSE @Status END

Answer 2

I thought you made a typo. It should be @State, not @Status. This simple query might not be what you are looking for since you want to two sql statements in your requirement.

SELECT * FROM MyTable
WHERE Type='AAA' AND (@State='--All--' or State=@State)

Answer 3

Or...

you could make it even simpler than that:

 SELECT * FROM MyTable
 WHERE Type='AAA' AND @State in ('--All--', State)

No need to do it in a stored procedure, unless absolutely necessary (or if business/coding practice requires you to do so).