词汇解析(
RDMBS:关系数据库管理系统(Relational Database Management System)
SELECT语句(
SELECT LastName FROM Presons /从Persons选取LastName列
SELECT * FROM Persons /从Persons选取所有列
SELECT DISTINCT Company FROM Orders /如需从 Company" 列中仅选取唯一不同的值,我们需要使用 SELECT DISTINCT 语句
SELECT * FROM Persons WHERE FirstName='Bush' /Persons是表名,FirstName是列名,Bush是值
SELECT * FROM Persons WHERE FirstName='Thomas' AND LastName='Carter' /使用AND表示2个条件并
SELECT * FROM Persons WHERE FirstName='Thomas' OR LastName='Carter' /使用OR表示2个条件或
SELECT * FROM Persons WHERE (FirstName='Thomas' OR FirstName='William') AND LastName='Carter'
)
ORDER BY语句(用于根据指定的列队结果集进行排序,默认按照升序。如果希望按照降序进行,可以使用DESC关键字
SELECT Company,OrderNumber FROM Orders ORDER BY Company /按照Company列升序排
SELECT Company,OrderNumber FROM Orders ORDER BY Company DESC /按照Company列降序排
SELECT Company,OrderNumber FROM Orders ORDER BY Company DESC,OrderNumber ASC /以逆字母顺序显示公司名称,并以数字顺序显示顺序号
)
INSERT INTO语句(
INSERT INTO 表名称 VALUES (值1,值2,......)
INSERT INTO 表名称 (列1,列2,.....) VALUES (值1,值2,......)
)
Update语句(
UPDATE 表名称 SET 列名称 = 新值 WHERE 列名称=某值
UPDATE Person SET Firstname = 'Will' Where Lastname = 'BOB' /更改1个列
UPDATE Person SET Address = 'Zhongshan 23' , City = 'NanJing' WHERE Lastname = 'Will'
)
Delete语句(
DELETE FROM Person WHERE LastName = 'Wilson' /删除某一行
DELETE FROM table_name或DELETE * FROM table_name /在不删除表的情况下,删除所有行
)
再1节学习TOP语句,配置测试库一起做实验
)