从2个表中获得修改结果

Question

我有两张桌子：

表1

id  |   name
-----------------------------------------
1   |   abc
2   |   def

表2

table1id    |   nr_name |   nr_val
-----------------------------------------
1           |   7       |   123
1           |   9       |   321
2           |   7       |   432

获得此结果需要哪些SQL代码？

结果

id  |   name    |   nr7 |   nr9
-----------------------------------------
1   |   abc     |   123 |   321
2   |   def     |   432 |   0

nr_name只能是7或9，我无法更改table2的结构 （我稍后会添加更多nr_name类型。）

Answer 1

试试这个：

sELECT 
  t1.id,
  t1.name,
  MAX(CASE WHEN t2.nr_name = 7 THEN t2.nr_val END) AS 'nr7',
  MAX(CASE WHEN t2.nr_name = 9 THEN t2.nr_val END) AS 'nr9'
FROM table1 AS t1
INNER JOIN  table2 AS t2 ON t1.id = t2.table1id
WHERE t2.name IN (7, 9)
GROUP BY t1.id, t1.name

Answer 2

SELECT t1.id,t1.name,
       CASE WHEN t2.nr_name = 7 THEN t2.nr_val ELSE 0 END AS 'nr7',
       CASE WHEN t2.nr_name = 9 THEN t2.nr_val ELSE 0 END AS 'nr9'
FROM table1 AS t1
INNER JOIN  table2 AS t2 ON t1.id = t2.table1id
WHERE t2.name IN (7,9)
GROUP BY t1.id, t1.name