如何组合2个mysql行并获得一行

Question

我有一张桌子report_card和，

示例数据如下。

report_id  orig_id   test_id        name     address
------------------------------------------------------
1           JH06E     IN2001         xyz      delhi
2           HL789     IN2001         abc      mumbai
3           ZPYNR     IN2002         pqr      mumbai
4           5R4HJ     IN2002         mno      delhi

我希望结果能得到孟买的所有行但是地址是德里而不是孟买？这里我有id 1和2有相同的test_id，3和4也有。输出如下，

report_id  orig_id   test_id        name     address
------------------------------------------------------
 2           HL789     IN2001         abc      delhi
 3           ZPYNR     IN2002         pqr      delhi

Answer 1

自我加入像：

SELECT t1.report_id, t1.orig_id, t1.test_id, t1.name, t2.address
FROM report_card t1
JOIN report_card t2
  ON t1.test_id = t2.test_id
WHERE
  t1.address = 'mumbai' AND
  t2.address = 'delhi'

Answer 2

@danblack写的是正确的，但要选择孟买的orig_id，你需要写下你的选择。

SELECT t1.report_id, 
       t2.orig_id, 
       t1.test_id, 
       t1.name, 
       t1.address 
FROM   mytable t1 
       INNER JOIN mytable t2 
               ON t1.test_id = t2.test_id 
WHERE  t1.address = 'delhi' 
       AND t2.address = 'mumbai' 

编辑：

对不起，我在问题上改变了我的结果，我可以得到孟买的所有行，但地址是德里而不是孟买

您也可以使用子查询执行此操作，如下所示。

SELECT t1.report_id, 
       t1.orig_id, 
       t1.test_id, 
       t1.name, 
       (SELECT address 
        FROM   mytable m 
        WHERE  m.test_id = t1.test_id 
               AND m.address = 'delhi' 
        LIMIT  1)AS address 
FROM   mytable t1 
WHERE  t1.address = 'mumbai' 

但是查看您的数据和预期结果，您只需要遵循以下内容即可

SELECT t1.report_id, 
       t1.orig_id, 
       t1.test_id, 
       t1.name, 
       'delhi' address 
FROM   mytable t1 
WHERE  t1.address = 'mumbai'