如何将 select 语句与另外两个 select 语句的联合

Question

table_a:

id	描述	类别
0	“等等等等”	类别 1
1	“很多话”	类别 1
2	“有用的描述”	类别 1
3	“非常高兴”	类别 1
4	“5 颗星”	类别 1
5	“不错”	类别 1
6	“不太好”	类别 1
7	“干得好”	类别 1
8	“印象不深”	类别 2
9	“还好”	类别 2

table_b:

id	数量	person_id	类型
0	000	00000000	b
1	100	11111111	b
2	200	22222222	b
3	300	33333333	b

table_c:

id	数量	person_id	类型
4	400	44444444	c
5	500	55555555	c
6	600	66666666	c
7	700	77777777	c

期望：

id	数量	person_id	类型	描述
0	000	00000000	b	“等等等等”
1	100	11111111	b	“很多话”
2	200	22222222	b	“有用的描述”
3	300	33333333	b	“非常高兴”
4	400	44444444	c	“5 颗星”
5	500	55555555	c	“不错”
6	600	66666666	c	“不太好”
7	700	77777777	c	“干得好”

以下在仅包含 t1 的行中给出了“SQL 命令未正确结束”。我知道这个错误与我如何为 table 添加别名有关，但我不确定下一步该怎么做。

SELECT 
    id, description
FROM 
    table_a
WHERE category = 'Category 1'
t1

LEFT JOIN

(
SELECT 
    id, num, person_id, type
FROM 
    table_b
UNION
SELECT 
    id, num, person_id, type
FROM 
    table_c
) t2
ON 
    t1.id = t2.id

Answer 1

此查询应该符合您的预期

SELECT   t1.id, t2.num, t2.person_id, t2.type, t2.description
FROM     table_a t1
LEFT JOIN 
(
    SELECT  id, num, person_id, type
    FROM    table_b
    UNION
    SELECT id, num, person_id, type
    from   table_c
) t2 on t1.id = t2.id
    
WHERE category = 'Category 1'

Answer 2

两个选项要么在子查询中使用 where 子句，要么在连接条件之后使用它。

SELECT 
    id, description
FROM 
    table_a
t1

LEFT JOIN

(
SELECT 
    id, num, person_id, type
FROM 
    table_b
UNION
SELECT 
    id, num, person_id, type
FROM 
    table_c
) t2
ON 
    t1.id = t2.id
WHERE t1.category = 'Category 1'

或

select * from (SELECT 
    id, description
FROM 
    table_a WHERE category = 'Category 1')
t1

LEFT JOIN

(
SELECT 
    id, num, person_id, type
FROM 
    table_b
UNION
SELECT 
    id, num, person_id, type
FROM 
    table_c
) t2
ON 
    t1.id = t2.id
WHERE t1.category = 'Category 1'

如何将 select 语句与另外两个 select 语句的联合

how to join a select statement with the union of two other select statements

sql

oracle

union

join

oracle-sqldeveloper