Question

这里有3个表，我想写一个SQL查询来从Table1和Table2获取Table3的值

Table1           
| ID  | NAME  |
+-----+-------+
| 111 | ALPHA |
| 222 | BRAVO |
+-----+-------+

Table2
| NAME_RESULT | STEP_ID | STEP_NAME | STEP_TYPE | STEP_PARENT |
+-------------+---------+-----------+-----------+-------------+
| 111         | aaa     |  R1       |  step2    |  5cf        |
| 222         | bbb     |  R2       |  step2    |  e7b        |
| 333         | ccc     |  R2       |  step2    |  3ac        | 
| 555         | e4a     |  C4       |  step10   |  51f        |
+-------------+---------+-----------+-----------+-------------+

Table2 we find on NAME_RESULT = 222 and STEP_ID = bbb --> STEP_PARENT = e7b Next reusing the previous STEP_ID from first STEP_PARENT values to get new STEP_PARENT :

| NAME_RESULT | STEP_ID | STEP_NAME  | STEP_TYPE | STEP_PARENT|
+-------------+---------+------------+-----------+------------+
| 111         | e7b     |  Measure R |  step2    |  89d       |
| 777         | 3ac     |  Measure R |  step2    |  5fc       |
+-------------+---------+------------+-----------+------------+

对于Table2的下一个查询，我们在STEP_ID = e7b - ＆gt;上找到了。 STEP_PARENT = 89d

Table3 on t3.IDM = t2.STEP_PARENT = 89d :

| IDM | MEAS  |
+-----+-------+
| eee | 10.1  |
+-----+-------+
| 89d | 12.2  |
| 5fc | 7.3   |
+-----+-------+    We find MEAS = 12.2

1）首先查询：

select * from Table1 t1 inner join Table2 t2 on t1.ID = t2.NAME_RESULT
where t2.STEP_NAME = 'R2' and t2.STEP_TYPE = 'step2' and 
t1.NAME = 'BRAVO'

- ＆GT;结果应为STEP_ID = bbb

2）第二次查询：

select * from Table2 t2 where t2.STEP_PARENT = STEP_ID

- ＆GT;结果应为STEP_ID = e7b

2）第三次查询：

select * from Table2 t2 where t2.STEP_ID = STEP_PARENT

- ＆GT;结果应为STEP_PARENT = 89d

3）上次查询：

select * from Table3 t3 inner join t2 on t2.STEP_PARENT = t3.IDM

- ＆GT; MEAS值应为= 12.2

希望它会更明确，所以请告诉我，如果可能的话，如何在一个查询中使用所有内容

感谢您的帮助

Answer 1

好的，我觉得这个问题很混乱。但希望这是您正在寻找的查询。

select
    t3.meas
from
    table3 t3
inner join
    table2 t2a
on t3.idm = t2a.step_parent
inner join
    table2 t2b
on t2a.step_id = t2b.step_parent
inner join
    table1 t1
on t2b.name_result = t1.id
where
    t1.name = 'BRAVO'
and t2b.step_name = 'R2'
and t2b.step_type = 'step2'

Answer 2

如果我理解正确，那么这应该有效。

select t3.MEAS from Table1 t1 
inner join Table2 t21 on t1.ID = t21.NAME_RESULT
inner join Table2 t22 on t21.STEP_PARENT  = t22.STEP_ID 
inner join Table3 t3 on t3.IDM = t22.STEP_PARENT
where t21.STEP_NAME = 'R2' and t21.STEP_TYPE = 'step2' and 
t1.NAME = 'BRAVO'

Answer 3

一步一步：

select meas
from table3
where idm =
(
  select step_parent
  from table2
  where step_id =
  (
    select step_parent
    from table2
    where name_result =
    (
      select id
      from table1
      where name = 'BRAVO'
    )
    and step_name = 'R2' 
    and step_type = 'step2'
  )
);

如果数据集中可以有多个条目，则可能必须将=替换为IN。

重用表的3个表上的SQL查询

3 个答案: