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SQLite ALIAS/别名

可以重命名表或列暂时给人的另一个名字,这被称为别名。使用表别名是指在一个特定的SQLite语句重命名表。重命名是一个临时的变化,并在数据库中实际的表的名称不会改变。

列别名用来重命名表中的列一个特定的SQLite查询的目的。

语法

表别名的基本语法如下:

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

列别名的基本语法如下:

SELECT column_name AS alias_name
FROM table_name
WHERE [condition];

例子:

考虑以下两个表:(一)COMPANY表如下:

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  45000.0
7           James                 24          Houston     10000.0

(b)另一表是DEPARTMENT如下:

ID          DEPT                  EMP_ID
----------  --------------------  ----------
1           IT Billing            1
2           Engineering           2
3           Finance               7
4           Engineering           3
5           Finance               4
6           Engineering           5
7           Finance               6

现在,下面是表的别名,在这里我们使用C和D分别为COMPANY和DEPARTMENT表的别名的用法:

sqlite> SELECT C.ID, C.NAME, C.AGE, D.DEPT
        FROM COMPANY AS C, DEPARTMENT AS D
        WHERE  C.ID = D.EMP_ID;

以上SQLite的语句将产生以下结果:

ID          NAME        AGE         DEPT
----------  ----------  ----------  ----------
1           Paul        32          IT Billing
2           Allen       25          Engineerin
3           Teddy       23          Engineerin
4           Mark        25          Finance
5           David       27          Engineerin
6           Kim         22          Finance
7           James       24          Finance

让我们看一个例子company_id的是ID列的别名和COMPANY_NAME的别名name列字段的别名的用法:

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;

以上SQLite的语句将产生以下结果:

COMPANY_ID  COMPANY_NAME  AGE         DEPT
----------  ------------  ----------  ----------
1           Paul          32          IT Billing
2           Allen         25          Engineerin
3           Teddy         23          Engineerin
4           Mark          25          Finance
5           David         27          Engineerin
6           Kim           22          Finance
7           James         24          Finance