SQLite ALIAS/彆名
可以重命名表或列暫時給人的另一個名字,這被稱為彆名。使用表彆名是指在一個特定的SQLite語句重命名表。重命名是一個臨時的變化,並在數據庫中實際的表的名稱不會改變。
列彆名用來重命名表中的列一個特定的SQLite查詢的目的。
語法
表彆名的基本語法如下:
SELECT column1, column2.... FROM table_name AS alias_name WHERE [condition];
列彆名的基本語法如下:
SELECT column_name AS alias_name FROM table_name WHERE [condition];
例子:
考慮以下兩個表:(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
現在,下麵是表的彆名,在這裡我們使用C和D分彆為COMPANY和DEPARTMENT表的彆名的用法:
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的語句將產生以下結果:
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
讓我們看一個例子company_id的是ID列的彆名和COMPANY_NAME的彆名name列字段的彆名的用法:
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的語句將產生以下結果:
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