Question

我需要你的帮助。我希望基于带有oracle SQL的第二个表来从同一个表中union数据。

表1

id | au_id | data
------------------
1  | 33    | foo
2  | 44    | foo
3  | 34    | foo
4  | 55    | foobar
5  | 55    | fooo

表2

au_id | follow_au_id
-----------------------
33    | 55

结果

au_id | data
----------------
33    | foo
33    | foobar
33    | fooo
44    | foo
34    | foo
55    | foobar
55    | fooo

Answer 1

你必须使用join

select t1.au_id, t3.data 
from table1 t1 
  join table2 t2 on t1.au_id=t2.au_id 
  join table1 t3 on t2.follow_au_id = t3.au_id
union     
select t1.au_id, t1.data 
from table1 t1

Answer 2

select au_id, data from tbl
union all
select t2.au_id, t1.data from tbl t1 join tbl t2 on t1.au_id = t2.follow_au_id

SQLFiddle

Answer 3

您需要加入和 UNION

SELECT t.*
FROM
  ( SELECT t1.au_id, t1.data FROM table1 t1
  UNION ALL
  SELECT t2.au_id,
    t1.data
  FROM table1 t1
  JOIN table2 t2
  ON t1.au_id = t2.follow_au_id
  ) t
ORDER BY t.au_id
/

感谢@notulysses指出，这是一个不正确的外连接解决方案。请参阅此SQL Fiddle。

正确的解决方案如下：

例如，

<强>设置

SQL> CREATE TABLE Table1
  2      (id int, au_id int, data varchar2(6))
  3  ;

Table created.

SQL>
SQL> INSERT ALL
  2      INTO Table1 (id, au_id, data)
  3           VALUES (1, 33, 'foo')
  4      INTO Table1 (id, au_id, data)
  5           VALUES (2, 44, 'foo')
  6      INTO Table1 (id, au_id, data)
  7           VALUES (3, 34, 'foo')
  8      INTO Table1 (id, au_id, data)
  9           VALUES (4, 55, 'foobar')
 10      INTO Table1 (id, au_id, data)
 11           VALUES (5, 55, 'fooo')
 12  SELECT * FROM dual
 13  ;

5 rows created.

SQL>
SQL> CREATE TABLE Table2
  2      (au_id int, follow_au_id int)
  3  ;

Table created.

SQL>
SQL> INSERT ALL
  2      INTO Table2 (au_id, follow_au_id)
  3           VALUES (33, 55)
  4  SELECT * FROM dual
  5  ;

1 row created.

SQL>

<强>查询

SQL> SELECT t.*
  2  FROM
  3    ( SELECT t1.au_id, t1.data FROM table1 t1
  4    UNION ALL
  5    SELECT t2.au_id,
  6      t1.data
  7    FROM table1 t1
  8    JOIN table2 t2
  9    ON t1.au_id = t2.follow_au_id
 10    ) t
 11  ORDER BY t.au_id
 12  /

     AU_ID DATA
---------- ------
        33 foobar
        33 fooo
        33 foo
        34 foo
        44 foo
        55 fooo
        55 foobar

7 rows selected.

SQL>

根据oracle的密钥从同一个表中选择联合表

3 个答案: