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
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
