sql 使用where筛选时,字段空时,不做筛选,非空时筛选

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需求说明:

1.查询“Name=赵” 且“Tel=180xxxxxxxx” 且“Address=西安预立数据科技有限责任公司“ 且“[email protected]”
2.当Name或Tel或Address或Email为空时不做筛选

方法一：

  这种方法可以达到目的，但是sql语句不易扩展和维护,不推荐使用 

  SELECT TOP 1000 [Id]
      ,[Name]
      ,[Tel]
      ,[Address]
      ,[Email]
  FROM [hlltest].[dbo].[User]
  WHERE 
  (name = @name AND  Tel IS NULL AND Address IS NULL AND Email IS NULL)
  OR (name IS NULL  AND  Tel = @Tel AND Address IS NULL AND Email IS NULL)
  OR (name IS NULL  AND  Tel IS NULL AND Address = @Address AND Email IS NULL)
  OR (name IS NULL  AND  Tel IS NULL AND Address IS NULL AND Email = @Email)

  OR (name = @name  AND  Tel = @Tel AND Address IS NULL AND Email IS NULL)
  OR (name = @name  AND  Tel IS NULL AND Address = @Address AND Email IS NULL)
  ---还有很多种组合条件.....

方法二：

  --推荐使用isnull 

DECLARE @name NVARCHAR(50) = '赵'
  ,@Tel NVARCHAR(50) = '180xxxxxxxx'
  ,@Address NVARCHAR(50) = '西安预立数据科技有限责任公司'
  ,@Email NVARCHAR(50) = '[email protected]'

  SELECT TOP 1000 [Id]
      ,[Name]
      ,[Tel]
      ,[Address]
      ,[Email]
  FROM [hlltest].[dbo].[User]
  WHERE ISNULL(name,@name) = @name
  AND ISNULL(Tel,@Tel) = @Tel
  AND ISNULL(Address,@Address) = @Address
  AND ISNULL(Email,@Email) = @Email

当Name,Tel,Address,Email存放是字符串空时，Isnull就不能使用, 可以使用case when 或 LEN 判断

方法一：

  --使用case when  

 DECLARE @name NVARCHAR(50) = '赵'
  ,@Tel NVARCHAR(50) = '180xxxxxxxx'
  ,@Address NVARCHAR(50) = '西安预立数据科技有限责任公司'
  ,@Email NVARCHAR(50) = '[email protected]'

  SELECT TOP 1000 [Id]
      ,[Name]
      ,[Tel]
      ,[Address]
      ,[Email]
  FROM [hlltest].[dbo].[User]
  WHERE (1 = (CASE WHEN Name = ''  THEN 1 ELSE 0 END) OR  Name = @name )
  AND (1 = (CASE WHEN Tel = ''  THEN 1 ELSE 0 END) OR  Tel = @Tel )
  AND (1 = (CASE WHEN Address = ''  THEN 1 ELSE 0 END) OR  Address = @Address )
  AND (1 = (CASE WHEN Email = ''  THEN 1 ELSE 0 END) OR  Email = @Email )

方法二：

--使用LEN  

DECLARE @name NVARCHAR(50) = '赵'
  ,@Tel NVARCHAR(50) = '180xxxxxxxx'
  ,@Address NVARCHAR(50) = '西安预立数据科技有限责任公司'
  ,@Email NVARCHAR(50) = '[email protected]'

  SELECT TOP 1000 [Id]
      ,[Name]
      ,[Tel]
      ,[Address]
      ,[Email]
  FROM [hlltest].[dbo].[User]
  WHERE (LEN(Name) = 0 OR  Name = @name )
  AND (LEN(Tel) = 0 OR  Tel = @Tel )
  AND (LEN(Address) = 0 OR  Address = @Address )
  AND (LEN(Email) = 0 OR  Email = @Email )