Question

SELECT S.Id, S.Name, S.Version, S.SoftNo
FROM SOFTWARE S WITH(NOLOCK)
WHERE (IF S.Version = 0 THEN S.Version > 0 ELSE S.Version = @Version)
AND (IF S.SoftNo = 0 THEN S.SoftNo > 0 ELSE S.SoftNo = @SoftNo)

如果Version等于零，我想列出所有版本号大于0但如果不等于0，那么Version应该是它的值。

SoftNo也是如此。

如何修复SQL查询。它只是不起作用。

更多详情：

这就是我想要实现的目标：

if(Version == 0)
{
     display every single rows if their version number is greater then 0;
}
else
{
     Lets assume that Version is equal to 5. Then just display the rows if their Version number is equal to 5;
} // This is like a C# code of what I am trying to do in my sql query.

Answer 1

您必须使用CASE WHEN语句而不是if

Answer 2

尝试这样的事情：

SELECT S.Id, S.Name, S.Version, S.SoftNo
FROM SOFTWARE S WITH(NOLOCK)
WHERE ((@Version = 0 AND S.Version > 0) OR 
       (@Version <> 0 AND S.Version = @Version)) AND 
      ((@SoftNo = 0 AND S.SoftNo > 0) OR 
       (@SoftNo <> 0 AND S.SoftNo = @SoftNo))

Answer 3

您是否考虑过使用SQL案例？

SELECT col1, col2,
    CASE
        WHEN expression THEN return 
        WHEN expression THEN return 
        ELSE return 
    END AS NameOfNewColWithReturnValues
FROM Col_FROM_WHICH_TABLE

Answer 4

不太明白，但如果你的意思是输入变量等于零，你可以这样做：

SELECT S.Id, S.Name, S.Version, S.SoftNo
FROM SOFTWARE S WITH(NOLOCK)
WHERE ((@Version = 0 AND S.Version > 0) OR (S.Version = @Version AND @Version > 0))
AND (@SoftNo = 0 AND S.SoftNo > 0) OR (@SoftNo = S.SoftNo AND @SoftNo > 0 )

Answer 5

相反，我想出了这个解决方法，

sSQL = @"SELECT S.Id, S.Name, S.Version, S.SoftNo
         FROM SOFTWARE S WITH(NOLOCK)
         WHERE 1 = 1";
// 1=1 is used just to list everything.

if(pVersion != 0)
{
     sSQL += " AND S.Version = @Version";
}
if(pSoftNo != 0)
{
     sSQL += " AND S.SoftNo = @SoftNo";
}

结论，如果将其他部分移至代码端。

Answer 6

为什么不

SELECT S.Id, S.Name, S.Version, S.SoftNo
FROM SOFTWARE S WITH(NOLOCK)
WHERE 
(
    (@Version = 0 OR (@Version <> 0 AND S.Version = @Version))
    AND
    (@SoftNo = 0 OR (@SoftNo <> 0 AND S.SoftNo = @SoftNo))
)

（你真的需要NOLOCK吗？）

Answer 7

不要使用连接的SQL，这是一种不良习惯，增加了SQL注入漏洞的可能性。您的SQL代码现在与以下（更安全）代码完全相同：

SELECT 
    S.Id, S.Name, S.Version, S.SoftNo
FROM
    SOFTWARE S WITH(NOLOCK)
WHERE
    (@Version = 0 OR @Version = S.Version)
    AND (@SoftNo = 0 OR @SoftNo = S.SoftNo)

SQL中的IF ELSE语句

7 个答案: