在 where 子句中不知道 LHS 和 RHS 的情况下编写 SQL 查询

Question

我有一个过滤器列表：[州、城市、大学]。

这里有几个过滤器：

'state' = "Tamil Nadu" / "Karnataka" / "Maharashtra" / "all"

过滤器

'city' = "Chennai" / "Kanyakumari" / "Madhurai" / "Bangalore" / "Mysore" / "Dharwad" / "Mumbai" / "Pune" / "all"

过滤器

" college" = any college in city / "all"

如果这些单个元素的值为“全部”，那么我不必将它们包含在 where 子句中。这意味着那些值不是“all”的元素必须包含在 where 子句中。

喜欢：

(If the filter "college" is "all")
Select college_name, branches from Colleges where state = state and city = city.

(If city and college is "all")
Select college_name, branches from Colleges where state= state.

(If all the filters have "all")
Select college_name, branches from Colleges.

如何做到这一点？请帮助我。

Answer 1

您可以通过在 where 子句中检查参数来跳过参数：

Select college_name, branches 
from Colleges 
where (state = 'all' or "state" = @state)
  and (city = 'all' or "city" = @city)