别名

可以暂时把表或列重命名为另一个名字，这被称为别名。使用表别名是指在一个特定的 SQLite 语句中重命名表。重命名是临时的改变，在数据库中实际的表的名称不会改变。

列别名用来为某个特定的 SQLite 语句重命名表中的列。

-- 表别名
SELECT column1, column2....
FROM table_name AS alias_name
WHERE [condition];

-- 列别名
SELECT column_name AS alias_name
FROM table_name
WHERE [condition];

实例

--数据准备
sqlite> select * from COMPANY ;
ID          NAME        AGE         ADDRESS     SALARY
----------  ----------  ----------  ----------  ----------
1           Paul        32          California  20000.0
2           Allen       25          Texas       15000.0
3           Teddy       23          Norway      20000.0
4           Mark        25          Rich-Mond   65000.0
5           David       27          Texas       85000.0
6           Kim         22          South-Hall
7           James       24          Houston
sqlite>
sqlite> select * from DEPARTMENT ;
ID          DEPT        EMP_ID
----------  ----------  ----------
1           IT Billing  1
2           Engineerin  2
3           Finance     7
4           Engineerin  3
5           Finance     4
6           Engineerin  5
7           Finance     6

-- 列别名
sqlite> SELECT C.ID, C.NAME, C.AGE, D.DEPT
   ...>         FROM COMPANY AS C, DEPARTMENT AS D
   ...>         WHERE  C.ID = D.EMP_ID;
ID          NAME        AGE         DEPT
----------  ----------  ----------  ----------
1           Paul        32          IT Billing
2           Allen       25          Engineerin
7           James       24          Finance
3           Teddy       23          Engineerin
4           Mark        25          Finance
5           David       27          Engineerin
6           Kim         22          Finance

-- 列别名
sqlite> SELECT C.ID AS COMPANY_ID, C.NAME AS COMPANY_NAME, C.AGE, D.DEPT
   ...>         FROM COMPANY AS C, DEPARTMENT AS D
   ...>         WHERE  C.ID = D.EMP_ID;
COMPANY_ID  COMPANY_NAME  AGE         DEPT
----------  ------------  ----------  ----------
1           Paul          32          IT Billing
2           Allen         25          Engineerin
7           James         24          Finance
3           Teddy         23          Engineerin
4           Mark          25          Finance
5           David         27          Engineerin
6           Kim           22          Finance