[英]How to Do a Query with Optional Search Parameters?
我的桌子上有这些栏;
Categ - int
WorkPlace - int
WorkPlace1 - int
AsignedAs - int
我正在使用C#
如果仅搜索参数之一不等于0,我想用OR
选择所有行。我添加了一个默认值,以了解用户是否从组合框中进行选择。
我想按此顺序与AND进行选择:如果多个搜索参数不等于0(用户选择值),则像这样
WHERE Categ = @categ AND WorkPlace = @WorkPlace (user select two values
其他为空或等于0
要么
WHERE WorkPlace = @WorkPlace AND WorkPlace1 = @WorkPlace1
要么
WHERE Categ = @Categ AND WorkPlace = @WorkPlace1
(用户选择这些值,并且不为空,因此我们在查询中添加and
)
等等....
所以我想检查值是否为空或不建立正确的查询。
请参阅Goran指出的用于处理可选值的链接-在这种情况下,如果用户未选择该选项,则需要将NULL传递给存储的proc。 如果您希望继续使用零(或其他某个值)来指示参数的不适用性,那么您可以修改查询,例如
WHERE
(COALESCE(@Categ, 0) = 0 OR Categ = @Categ) AND
(COALESCE(@WorkPlace, 0) = 0 OR WorkPlace = @WorkPlace) AND
(COALESCE(@WorkPlace1, 0) = 0 OR WorkPlace1 = @WorkPlace1) AND
(COALESCE(@AsignedAs, 0) = 0 OR AsignedAs= @AsignedAs)
希望您有大致的想法!
您也可以使用CASE方法。 我发现这非常有用且容易,并且SQL Query Optimizer似乎针对这种情况选择了更好的执行计划:
WHERE CASE WHEN @Categ = 0 THEN 0 ELSE Categ END = CASE WHEN @Categ = 0 THEN 0 ELSE @Categ END
AND CASE WHEN @WorkPlace = 0 THEN 0 ELSE WorkPlace END = CASE WHEN @WorkPlace = 0 THEN 0 ELSE @WorkPlace END
AND CASE WHEN @WorkPlace1 = 0 THEN 0 ELSE WorkPlace1 END = CASE WHEN @WorkPlace1 = 0 THEN 0 ELSE @WorkPlace1 END
AND CASE WHEN @AsignedAs = 0 THEN 0 ELSE AsignedAs END = CASE WHEN @AsignedAs = 0 THEN 0 ELSE @AsignedAs END
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