如何根据参数值设置条件where子句

Question

我有以下SQL，

DECLARE @EmployeeID Int

SELECT *
  FROM [Northwind].[dbo].[Orders]
  WHERE OrderID = 10248
  AND EmployeeID = @EmployeeID

我想确保IF @EmployeeID IS NULL然后不要包含AND

类似的东西，

SELECT *
  FROM [Northwind].[dbo].[Orders]
  WHERE OrderID = 10248
  IF @EmployeeID IS NOT  NULL
  AND EmployeeID = @EmployeeID

我可以考虑创建一个表变量，然后根据参数值对它们进行过滤，但是有更好的方法吗？

Answer 1

我想你想要：

WHERE OrderID = 10248 AND
      (@EmployeeId IS NULL OR EmployeeID = @EmployeeID)

Answer 2

DECLARE @EmployeeID Int

SELECT *
  FROM [Northwind].[dbo].[Orders]
  WHERE OrderID = 10248
  AND EmployeeID = ISNULL(@EmployeeID, EmployeeID )