mysql LEFT JOIN多表連接查詢

具體操作

MySQL支援Select和某些Update和Delete情況下的Join文法，具體文法上的細節有：
 table_references:
    table_reference [, table_reference] …
 table_reference:
    table_factor
  | join_table
 table_factor:
    tbl_name [[AS] alias]
        [{USE|IGNORE|FORCE} INDEX (key_list)]
  | ( table_references )
  | { OJ table_reference LEFT OUTER JOIN table_reference
        ON conditional_expr }
 join_table:
    table_reference [INNER | CROSS] JOIN table_factor [join_condition]
  | table_reference STRAIGHT_JOIN table_factor
  | table_reference STRAIGHT_JOIN table_factor ON condition
  | table_reference LEFT [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [LEFT [OUTER]] JOIN table_factor
  | table_reference RIGHT [OUTER] JOIN table_reference join_condition
  | table_reference NATURAL [RIGHT [OUTER]] JOIN table_factor
 join_condition:
    ON conditional_expr | USING (column_list)

除了常用的兩個表串連之外，SQL（MySQL） JOIN 文法還支援多表串連。多表串連基本文法如下：

... FROM table1 INNER|LEFT|RIGHT JOIN table2 ON condition INNER|LEFT|RIGHT JOIN table3 ON condition ...

JOIN 多表串連實現了從多個表中擷取相關資料，下面是三個未經處理資料表：

article 文章表:

aid	title	content	uid	tid
1	文章1	文章1本文內容...	1	1
2	文章2	文章2本文內容...	1	2
3	文章3	文章3本文內容...	2	1
5	文章5	文章5本文內容...	4	1

user 使用者表:

uid	username	email
1	admin	admin@5idev.com
2	小明	xiao@163.com
3	Jack	jack@gmail.com

type 文章類型表:

tid	typename
1	普通文章
2	精華文章
3	草稿

代碼如下	複製代碼
SELECT * FROM t1 LEFT JOIN (t2, t3, t4) ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)