sqlite

database; ?? ??? ??????

unions

n. Union; ??? ???;

SQLite Unions ?? ???

??: SQLite? UNION ?/???? ??? ?? ???? ?? ? ? ??? SELECT ?? ??? ???? ? ?????.

UNION? ????? ? SELECT?? ??? ?? ??, ? ???? ??, ??? ??? ???? ?? ??? ???? ??? ??? ?? ??? ????. ?? ??.

??: ??UNION? ?? ??? ??? ????.

SELECT ??1 [, ??2 ]
FROM table1 [, table2 ]
[WHERE ??]

UNION

SELECT ??1 [, ??2 ]
FROM table1 [ , table2 ]
[WHERE ??]

??? ??? ??? ??? ?? ?? ??? ?????.

SQLite Unions ?? ?

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)另一個(gè)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
現(xiàn)在,讓我們使用 SELECT 語句及 UNION 子句來連接兩個(gè)表,如下所示:

sqlite> SELECT EMP_ID, NAME, DEPT FROM COMPANY INNER JOIN DEPARTMENT
        ON COMPANY.ID = DEPARTMENT.EMP_ID
   UNION
     SELECT EMP_ID, NAME, DEPT FROM COMPANY LEFT OUTER JOIN DEPARTMENT
        ON COMPANY.ID = DEPARTMENT.EMP_ID;
這將產(chǎn)生以下結(jié)果:

EMP_ID      NAME                  DEPT
----------  --------------------  ----------
1           Paul                  IT Billing
2           Allen                 Engineerin
3           Teddy                 Engineerin
4           Mark                  Finance
5           David                 Engineerin
6           Kim                   Finance
7           James                 Finance