WHERE 子句中的可选参数

Question

让我们假设有一个具有 3 个参数的存储过程。在所有的可能性中，我希望通过一个 WHERE 子句来实现这一点，而不会因为过多地使用 () AND () OR () 而失控......

例子：

    //Params
@CITY VARCHAR(100) = NULL,
@GENDER VARCHAR(100) = NULL,
@AGE VARCHAR(100) = NULL

我想你可以为每个变量使用IF BEGIN ... END 如果存在，但这会使代码比预期的要长很多..

下面的这个方法行不通，因为它太长了（大约有 10 个这样的不同字段，但示例只有 3 个。）而且我不确定它是否直接提取了独特的值......

SELECT NAME FROM TABLE 
WHERE (
(CITY=@CITY AND GENDER=@GENDER AND AGE=@AGE)
OR (CITY=@CITY AND GENDER=@GENDER)
OR (GENDER=@GENDER AND AGE=@AGE)
OR (CITY=@CITY AND AGE=@AGE)
OR (CITY=@CITY)
OR (GENDER=@GENDER)
OR (AGE=@AGE)
)

有没有更短更有效的方法来做到这一点？

如果是，该方法最好也与 JOIN 兼容。

Answer 1

除了ISNULL / COALESCE 选项，您可以测试参数是否为空：

SELECT NAME  
FROM TABLE  
WHERE  
    (@City IS NULL OR City = @City)
AND 
    (@Gender IS NULL OR Gender = @Gender)
AND 
    (@Age IS NULL OR Age = @Age) 

Answer 2

这个呢？

SELECT
    NAME
FROM TABLE 
WHERE CITY = COALESCE(@CITY, CITY)
    AND GENDER = COALESCE(@GENDER, GENDER)
    AND AGE = COALESCE(@AGE, AGE)

Answer 3

试试这样的：

SELECT NAME 
FROM TABLE 
WHERE 
    City = IsNull(@City, City) AND
    Gender = IsNull(@Gender, Gender) AND
    Age = IsNull(@Age, Age)

或者：

SELECT NAME 
FROM TABLE 
WHERE 
    (City = @City OR @City IS NULL) AND
    (Gender = @Gender OR @Gender IS NULL) AND
    (Age = @Age OR @Age IS NULL)

Answer 4

SELECT NAME   
FROM TABLE   
WHERE       
  City = case when isnull(@City ,'') = '' then City
                        else @City end
AND      
  Gender = case when isnull(@Gender ,'') = '' then Gender
                        else @Gender end
AND  
  Age = case when isnull(@Age ,0) = 0 then Age
                        else @Age end    

Answer 5

可能是这样的：

create procedure myProc
    --Params
@CITY VARCHAR(100) = NULL,
@GENDER VARCHAR(100) = NULL,
@AGE VARCHAR(100) = NULL
as

SELECT NAME FROM [TABLE]
WHERE ISNULL(CITY,'')=ISNULL(@CITY,ISNULL(CITY,''))
AND ISNULL(GENDER,'')=ISNULL(@GENDER,ISNULL(GENDER,''))
AND ISNULL(AGE,'')=ISNULL(@AGE,ISNULL(AGE,''))
go

假设 WHERE 子句中的列可以为空，使用 ISNULL 避免空比较。