Alias
用途：
可用在表、结果集或者列上，为它们取一个逻辑名称
语法：
给列取别名：
SELECT column AS column_alias FROM table |
给表取别名：
SELECT column FROM table AS table_alias |
例：
“Persons”表中的原始数据:
|
LastName |
FirstName |
Address |
City |
|
Hansen |
Ola |
Timoteivn 10 |
Sandnes |
|
Svendson |
Tove |
Borgvn 23 |
Sandnes |
|
Pettersen |
Kari |
Storgt 20 |
Stavanger |
运行下面的SQL：
SELECT LastName AS Family, FirstName AS Name FROM Persons |
返回结果：
|
Family |
Name |
|
Hansen |
Ola |
|
Svendson |
Tove |
|
Pettersen |
Kari |
运行下面的SQL：
SELECT LastName, FirstName FROM Persons AS Employees |
返回结果：
Employees中的数据有：
|
LastName |
FirstName |
|
Hansen |
Ola |
|
Svendson |
Tove |
|
Pettersen |
Kari |
Insert Into
用途：
在表中插入新行
语法：
插入一行数据
INSERT INTO table_name VALUES (value1, value2,....) |
插入一行数据在指定的字段上
INSERT INTO table_name (column1, column2,...) VALUES (value1, value2,....) |
例：
“Persons”表中的原始数据:
|
LastName |
FirstName |
Address |
City |
|
Pettersen |
Kari |
Storgt 20 |
Stavanger |
运行下面的SQL插入一行数据：
INSERT INTO Persons VALUES ('Hetland', 'Camilla', 'Hagabakka 24', 'Sandnes') |
插入后”Persons”表中的数据为：
|
LastName |
FirstName |
Address |
City |
|
Pettersen |
Kari |
Storgt 20 |
Stavanger |
|
Hetland |
Camilla |
Hagabakka 24 |
Sandnes |
运行下面的SQL插入一行数据在指定的字段上：
INSERT INTO Persons (LastName, Address) VALUES ('Rasmussen', 'Storgt 67') |
插入后”Persons”表中的数据为：
|
LastName |
FirstName |
Address |
City |
|
Pettersen |
Kari |
Storgt 20 |
Stavanger |
|
Hetland |
Camilla |
Hagabakka 24 |
Sandnes |
|
Rasmussen |
|
Storgt 67 |
|
Update
用途：
更新表中原有数据
语法：
UPDATE table_name SET column_name = new_value WHERE column_name = some_value |
例：
“Person”表中的原始数据:
|
LastName |
FirstName |
Address |
City |
|
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
|
Rasmussen |
|
Storgt 67 |
|
运行下面的SQL将Person表中LastName字段为”Rasmussen”的FirstName更新为”Nina”：
UPDATE Person SET FirstName = 'Nina' WHERE LastName = 'Rasmussen' |
更新后”Person”表中的数据为：
|
LastName |
FirstName |
Address |
City |
|
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
|
Rasmussen |
Nina |
Storgt 67 |
|
同样的，用UPDATE语句也可以同时更新多个字段：
UPDATE Person SET Address = 'Stien 12', City = 'Stavanger' WHERE LastName = 'Rasmussen' |
更新后”Person”表中的数据为：
|
LastName |
FirstName |
Address |
City |
|
Nilsen |
Fred |
Kirkegt 56 |
Stavanger |
|
Rasmussen |
Nina |
Stien 12 |
Stavanger |
|
