Question

我遇到了MS SQL Server 2008的问题：

当我使用硬编码字符串作为参数执行查询时，我的查询运行得很快但是当我使用字符串参数时，查询需要更长时间！
常量字符串查询需要1秒，而另一个需要11秒。

以下是代码：

常量字符串（1秒）：

     SELECT * 
FROM   VIEWCONTENTS 
WHERE  COUNTRY = 'ZA' 
       AND CONTENTTYPE = 'A' 
       AND TASK = 'R23562';

参数化（11秒）：

DECLARE @country AS CHAR(2); 

SET @country = 'ZA'; 

SELECT * 
FROM   VIEWCONTENTS 
WHERE  COUNTRY = @country 
       AND CONTENTTYPE = 'A' 
       AND TASK = 'R23562'

Answer 1

在查询结尾处使用 OPTION（RECOMPILE）。所以：

DECLARE @country AS CHAR(2); 

SET @country = 'ZA'; 

SELECT * 
FROM   VIEWCONTENTS 
WHERE  COUNTRY = @country 
       AND CONTENTTYPE = 'A' 
       AND TASK = 'R23562'
OPTION (RECOMPILE)

Answer 2

这会产生什么结果？

DECLARE @country AS VARCHAR(2); 
SET @country = 'ZA'; 

SELECT * 
FROM   VIEWCONTENTS 
WHERE  COUNTRY = @country 
       AND CONTENTTYPE = 'A' 
       AND TASK = 'R23562'

这个怎么样？

DECLARE @country AS CHAR(2); 
DECLARE @country1 AS VARCHAR(2); 
SET @country = 'ZA';
SET @country1 = @country; 

SELECT * 
FROM   VIEWCONTENTS 
WHERE  COUNTRY = @country 
       AND CONTENTTYPE = 'A' 
       AND TASK = 'R23562'

SQL Server查询使用参数比使用常量字符串花费更长时间

2 个答案: