SQLite 别名语法
你可以通过提供另一个名称来临时重命名表或列,该名称称为别名(ALIAS)。表别名的使用意味着在特定的SQLite语句中重命名表。重命名是一个临时更改,数据库中的实际表名不会更改。
列别名用于重命名表的列,以用于特定的SQLite查询。
语法
以下是给表起别名的基本语法:
SELECT column1, column2.... FROM table_name AS alias_name WHERE [condition];
以下是给列起别名的基本语法:
SELECT column_name AS alias_name FROM table_name WHERE [condition];
例子
考虑以下两个表,(a) COMPANY 表格如下:
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)另一张桌子是 部门 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,以下是我们分别使用C和D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语句将产生以下结果:
ID NAME AGE DEPT ---------- ---------- ---------- ---------- 1 Paul 32 IT Billing 2 Allen 25 Engineering 3 Teddy 23 Engineering 4 Mark 25 Finance 5 David 27 Engineering 6 Kim 22 Finance 7 James 24 Finance
其中COMPANY_ID是ID列的别名,而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语句将产生以下结果:
COMPANY_ID COMPANY_NAME AGE DEPT ---------- ------------ ---------- ---------- 1 Paul 32 IT Billing 2 Allen 25 Engineering 3 Teddy 23 Engineering 4 Mark 25 Finance 5 David 27 Engineering 6 Kim 22 Finance 7 James 24 Finance