使用Join / coalesce更新语句以在gridview上显示数据

Question

我正在使用在gridview上使用的查询来选择要显示的数据：

SELECT [Theme].[PK_Theme], [Theme].[Name], [ThemeType].[Type] 
FROM [Theme] 
LEFT OUTER JOIN [ThemeType] 
ON [Theme].[ThemeTypeId] = [ThemeType].[PK_ThemeType] 
JOIN [ProductTheme] ON [ProductTheme].[ThemeId]=[Theme].[PK_Theme] 
WHERE ProductTheme.ProductID LIKE @productParam 
AND ProductTheme.ThemeId = Theme.PK_Theme 
AND COALESCE([THEME].[THEMETYPEID], 'null') LIKE @assignedParam 
GROUP BY [Theme].[Name], [ThemeType].[Type], [Theme].[PK_Theme] 
ORDER BY CASE WHEN [ThemeType].[Type] IS NULL THEN 0 ELSE 1 END, [Theme].[Name]

列[THEME]。[THEMETYPEID]以前是varchar（50）但已更改为int。

我现在收到此错误：

Conversion failed when converting the varchar value 'NULL' to data type int.

有一点奇怪的是，我直接查询服务器上面的语句是否有效，（我更改了值的参数）但是它在服务器控件中不起作用。

更新后的列允许空值。如何在这种情况下检查一个int的Null并让查询像以前一样工作？

编辑如果两个参数都分配了'％'，我希望结果如下：

Answer 1

这一行：

AND COALESCE([THEME].[THEMETYPEID], 'null') LIKE @assignedParam 

应该是（没有单引号）：

AND COALESCE([THEME].[THEMETYPEID], NULL) LIKE @assignedParam 

因为'null'是普通字符串，而您可能打算表示NULL值

或许您应该将其更改为：

AND COALESCE([THEME].[THEMETYPEID], 0) LIKE @assignedParam 

由于ThemeTyeID是一个i​​nt

<强>更新

试试这个：

 SELECT  [Theme].[PK_Theme] ,
                [Theme].[Name] ,
                [ThemeType].[Type]
        FROM    [Theme]
                LEFT OUTER JOIN [ThemeType] ON [Theme].[ThemeTypeId] = [ThemeType].[PK_ThemeType]
                JOIN [ProductTheme] ON [ProductTheme].[ThemeId] = [Theme].[PK_Theme]
        WHERE   ProductTheme.ProductID LIKE @productParam
                AND ProductTheme.ThemeId = Theme.PK_Theme
                AND 1 = CASE WHEN [THEME].[THEMETYPEID] IS NULL THEN 1
                             WHEN [THEME].[THEMETYPEID] LIKE @param THEN 1
                        END
        GROUP BY [Theme].[Name] ,
                [ThemeType].[Type] ,
                [Theme].[PK_Theme]
        ORDER BY CASE WHEN [ThemeType].[Type] IS NULL THEN 0
                      ELSE 1
                 END ,
                [Theme].[Name]

但是我们警告说，如果这样可以按照您的意愿工作，那么它就不如为每个案例编写单独的查询一样有效。也许和他们结合......

Answer 2

请尝试以下代码：

SELECT [Theme].[PK_Theme], [Theme].[Name], [ThemeType].[Type] 
FROM [Theme] 
LEFT OUTER JOIN [ThemeType] 
ON [Theme].[ThemeTypeId] = [ThemeType].[PK_ThemeType] 
JOIN [ProductTheme] ON [ProductTheme].[ThemeId]=[Theme].[PK_Theme] 
WHERE ProductTheme.ProductID LIKE @productParam 
AND ProductTheme.ThemeId = Theme.PK_Theme AND [Theme].[ThemeTypeId] IS NOT NULL 
AND COALESCE([THEME].[THEMETYPEID], 'null') LIKE @assignedParam 
GROUP BY [Theme].[Name], [ThemeType].[Type], [Theme].[PK_Theme] 
ORDER BY CASE WHEN [ThemeType].[Type] IS NULL THEN 0 ELSE 1 END, [Theme].[Name]