Select 所有行如果@Parameter = NULL

Question

我有一个带参数的存储过程，@PolicySymbol，它可以接受多个值。为此，我使用了一个拆分字符串函数：StringOfStringsToTable

如果用户选择 @ControlNo，那么无论为 @PolicySymbol 设置什么值，我都想为 controlNo 带来数据。

If @PolicySymbol = NULL 我想为 controlNo 带来所有数据，无论它与什么政策符号相关。

这是代码示例：

CREATE TABLE #Test (ControlNo int, policy_symbol varchar(50))

INSERT INTO #Test 
VALUES (1111, 'CSE'), (2222, 'PRE'), (3333, 'CSE'), (4444, 'GLG'),
       (4444, 'PRE'), (4444, 'GLS') 

DECLARE 
    @ControlNo int = 1111,
    @PolicySymbol varchar(50) = NULL 

SELECT DISTINCT ControlNo, policy_symbol
FROM #Test
WHERE ControlNo = COALESCE(@ControlNo, ControlNo)
 -- here, if parameter @PolicySymbol IS NULL I want to include all policy symbols
  AND policy_symbol IN (SELECT String FROM [dbo].[StringOfStringsToTable] (@PolicySymbol, ','))

DROP TABLE #Test

Answer 1

一个简单、合乎逻辑的 OR 就可以了。

WHERE ControlNo = COALESCE(@ControlNo, ControlNo)
-- If parameter @PolicySymbol IS NULL I want to include all policy symbols
AND (
    @PolicySymbol IS NULL
    OR policy_symbol IN (SELECT String FROM [dbo].[StringOfStringsToTable] (@PolicySymbol,','))
)

Select 所有行如果@Parameter = NULL

Select all rows if @Parameter = NULL

tsql

sql-server

stored-procedures

sql-server-2017