存储过程：如果不存在记录，则运行不同的选择答案

【问题标题】：Stored procedure: if no record exists run different select存储过程：如果不存在记录，则运行不同的选择
【发布时间】：2018-03-06 20:27:12
【问题描述】：

在我的存储过程中，我有以下语句：

SELECT TOP 200 
    C.CustomerNumber,
    C.CustomerName,
    C.AccountManager,
    C.CustomerId        
FROM 
    Customer C WITH(NOLOCK, index (UQ_Customer_CustomerNumber))
LEFT JOIN 
    CustomerQuotingPreference cp WITH(NOLOCK) ON cp.CustomerId = C.CustomerId
WHERE  
    (C.CustomerName LIKE ('%' +  @searchString + '%') 
    OR C.CustomerNumber LIKE ('%' + CONVERT(VARCHAR(61), @searchString) + '%')))
ORDER BY
    C.CustomerName

我现在想检查一下，如果此选择没有返回任何记录，请运行不同的选择。

【问题讨论】：

看看@@ROWCOUNTdocs.microsoft.com/en-us/sql/t-sql/functions/…
设置Bad Habits to kick - putting NOLOCK everywhere - 不建议在任何地方都使用它 - 恰恰相反！
通常我将这种逻辑放在应用程序代码中。
NOLOCK 在某些边缘情况下有意义......但我怀疑这是其中之一，尤其是如果你想要干净的数据！

标签： sql sql-server-2008 stored-procedures

【解决方案1】：

DECLARE @Temp Table
(
    CustomerNumber VarChar, //or whatever type these are
    CustomerName   VarChar,
    AccountManager VarChar,
    CustomerId     Int
)

INSERT INTO @Temp
SELECT TOP 200  
    C.CustomerNumber,
    C.CustomerName,
    C.AccountManager,
    C.CustomerId        
FROM 
    Customer C WITH(NOLOCK, index (UQ_Customer_CustomerNumber))
LEFT JOIN 
    CustomerQuotingPreference cp WITH(NOLOCK) ON cp.CustomerId = C.CustomerId
WHERE  
    (C.CustomerName LIKE ('%' +  @searchString + '%') 
    OR C.CustomerNumber LIKE ('%' + CONVERT(VARCHAR(61), @searchString) + '%')))
ORDER BY
    C.CustomerName

IF @@ROWCOUNT <> 0
    BEGIN
        SELECT * FROM @Temp
        RETURN
    END

SELECT * FROM OtherTable

【讨论】：

【解决方案2】：

我更喜欢这种方式

if exists (
    SELECT 1
    FROM 
        Customer C WITH(NOLOCK, index (UQ_Customer_CustomerNumber))
    LEFT JOIN 
        CustomerQuotingPreference cp WITH(NOLOCK) ON cp.CustomerId = C.CustomerId
    WHERE  
        (C.CustomerName LIKE ('%' +  @searchString + '%') 
        OR C.CustomerNumber LIKE ('%' + CONVERT(VARCHAR(61), @searchString) + '%')))
)

SELECT TOP 200  
    C.CustomerNumber,
    C.CustomerName,
    C.AccountManager,
    C.CustomerId        
FROM 
    Customer C WITH(NOLOCK, index (UQ_Customer_CustomerNumber))
LEFT JOIN 
    CustomerQuotingPreference cp WITH(NOLOCK) ON cp.CustomerId = C.CustomerId
WHERE  
    (C.CustomerName LIKE ('%' +  @searchString + '%') 
    OR C.CustomerNumber LIKE ('%' + CONVERT(VARCHAR(61), @searchString) + '%')))
ORDER BY
    C.CustomerName;
else
    SELECT * FROM OtherTable;

【讨论】：