关系运算符

运算符	含义
`=`	等于
`<>`	不等于
`>`	大于
`>=`	大于或等于
`<`	小于
`<=`	小于或等于
`LIKE`	匹配模式
`NOT LIKE`	不匹配模式
`IS NULL`	等于 Null
`IS NOT NULL`	不等于 Null
`BETWEEN`	下限和上限之间值的范围
`IN`	一组指定值的成员或子查询的成员
`NOT IN`	并非一组指定值的成员或子查询的成员
`EXISTS`	如果子查询返回至少一个记录，则为“True”
`ANY`	将某个值与子查询返回的每个值进行比较（运算符前面必须是 =、<>、>、>=、< 或 <=）；=Any 相当于 In
`ALL`	将某个值与子查询返回的每个值进行比较（运算符前面必须是 =、<>、>、>=、< 或 <=）

示例

复制

SELECT Sales_Data.Invoice_ID FROM Sales_Data
   WHERE Sales_Data.Salesperson_ID = 'SP-1'
   
SELECT Sales_Data.Amount FROM Sales_Data WHERE Sales_Data.Invoice_ID <> 125

SELECT Sales_Data.Amount FROM Sales_Data WHERE Sales_Data.Amount > 3000

SELECT Sales_Data.Time_Sold FROM Sales_Data
   WHERE Sales_Data.Time_Sold < '12:00:00'

SELECT Sales_Data.Company_Name FROM Sales_Data
   WHERE Sales_Data.Company_Name LIKE '%University'

SELECT Sales_Data.Company_Name FROM Sales_Data
   WHERE Sales_Data.Company_Name NOT LIKE '%University'

SELECT Sales_Data.Amount FROM Sales_Data WHERE Sales_Data.Amount IS NULL

SELECT Sales_Data.Amount FROM Sales_Data WHERE Sales_Data.Amount IS NOT NULL

SELECT Sales_Data.Invoice_ID FROM Sales_Data
   WHERE Sales_Data.Invoice_ID BETWEEN 1 AND 10

SELECT COUNT(Sales_Data.Invoice_ID) AS agg
   FROM Sales_Data WHERE Sales_Data.INVOICE_ID IN (50,250,100)

SELECT COUNT(Sales_Data.Invoice_ID) AS agg
   FROM Sales_Data WHERE Sales_Data.INVOICE_ID NOT IN (50,250,100)

SELECT COUNT(Sales_Data.Invoice_ID) AS agg FROM Sales_Data 
   WHERE Sales_Data.INVOICE_ID NOT IN (SELECT Sales_Data.Invoice_ID
   FROM Sales_Data WHERE Sales_Data.Salesperson_ID = 'SP-4')

SELECT *
   FROM Sales_Data WHERE EXISTS (SELECT Sales_Data.Amount
   FROM Sales_Data WHERE Sales_Data.Salesperson_ID IS NOT NULL)

SELECT *
   FROM Sales_Data WHERE Sales_Data.Amount = ANY (SELECT Sales_Data.Amount
   FROM Sales_Data WHERE Sales_Data.Salesperson_ID = 'SP-1')

SELECT *
   FROM Sales_Data WHERE Sales_Data.Amount = ALL (SELECT Sales_Data.Amount
   FROM Sales_Data WHERE Sales_Data.Salesperson_ID IS NULL)