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이 문서에서는 PHP 중국어 웹사이트 매뉴얼 풀어 주다
您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];
假设有下面两个表,(1)COMPANY 表如下所示:
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
(2)另一个表是 DEPARTMENT,如下所示:
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 表别名 的用法,在这里我们使用 C 和 D 分别作为 COMPANY 和 DEPARTMENT 表的别名:
sqlite> SELECT C.ID, C.NAME, C.AGE, D.DEPT FROM COMPANY AS C, DEPARTMENT AS D WHERE C.ID = D.EMP_ID;
上面的 SQLite 语句将产生下面的结果:
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 列别名 的实例,在这里 COMPANY_ID 是 ID 列的别名,COMPANY_NAME 是 name 列的别名:
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;
上面的 SQLite 语句将产生下面的结果:
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