SQL.
SELECT 列名称 FROM 表名称 如：1. SELECT LastName,FirstName FROM Persons2. SELECT * FROM Persons
SQL SELECT DISTINCT 语句在表中，可能会包含重复值。仅列出不同（distinct）的值。关键词 DISTINCT 用于返回唯一不同的值。 如： SELECT DISTINCT Company FROM Orders
SELECT 列名称 FROM 表名称 WHERE 列 运算符 值 如：1. SELECT * FROM Persons WHERE City='Beijing' 2. SELECT * FROM Persons WHERE Year>1965 3. SELECT * FROM Persons WHERE LastName BETWEEN 'Adams' AND 'Carter'4. SELECT * FROM Persons WHERE City LIKE 'N%'5. SELECT * FROM Persons WHERE City NOT LIKE '%lon%'6. SELECT * FROM Persons WHERE FirstName='Thomas' AND LastName='Carter'7. SELECT * FROM Persons WHERE FirstName='Thomas' OR LastName='Carter'
SQL ORDER BY 子句 ORDER BY 语句用于根据指定的列对结果集进行排序。ORDER BY 语句默认按照升序对记录进行排序。如果您希望按照降序对记录进行排序，可以使用 DESC 关键字。 如：1. SELECT Company, OrderNumber FROM Orders ORDER BY Company, OrderNumber2. SELECT Company, OrderNumber FROM Orders ORDER BY Company DESC
HAVING 子句 如： 现在我们希望查找客户 'Bush' 或 'Adams' 拥有超过 1500 的订单总金额。SELECT Customer,SUM(OrderPrice) FROM Orders WHERE Customer='Bush' OR Customer='Adams'GROUP BY CustomerHAVING SUM(OrderPrice)>1500
两个表应用select 如：SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons, Orders WHERE Persons.Id_P = Orders.Id_P
注释：SQL 语句对大小写不敏感。SELECT 等效于 select。
SQL 使用单引号来环绕文本值。如果是数值，请不要使用引号。