Question

我有一个table1 a_id表PK，ipaddress，create_dt 此处ipaddress为varchar，create_dt为datetime

a_id    ip              create_dt
9205    10.10.10.10     2017-01-07 08:03:32
9206    10.10.10.11     2017-01-06 08:03:32
9207    10.10.10.12     2015-01-07 08:03:32

---超过1000行

我有另一个mysql表，其中包含以下id列，PK，ip，check_type check_status，a_id和created_dt }：此处a_id是来自table1的外键 created_dt是datetime

id      ip             check_type    check_status  a_id    timestamp_val
1       10.10.10.10    check1        FAIL          9205    2017-01-07 10:03:32
2       10.10.10.10    check2        PASS          9205    2017-01-07 10:03:32
3       10.10.10.10    check1        FAIL          9205    2016-11-07 10:03:32
4       10.10.10.10    check2        PASS          9205    2016-11-07 10:03:32
5       10.10.10.11    check1        PASS          9206    2017-01-06 10:03:32
6       10.10.10.11    check2        PASS          9206    2015-01-06 10:03:32

我想要table1 date(create_dt) >= '2017-01-07'和table1.a_id = table2.a_id的所有行 table2.check1 = 'FAIL'和I only want to consider the row from table2 此外，timestamp_val最新a_id ip create_dt 9205 10.10.10.10 2017-01-07 08:03:32

所以从上面的例子中，我的查询应该返回

want to know how to incorporate the logic to consider the row from table2 with latest 'timestamp_val'

我写了以下查询和SELECT * FROM table1 a INNER JOIN table2 b ON a.a_id = b.a_id AND DATE(a.create_dt) >= '2017-01-07' AND b.check_status = 'FAIL' AND b.check_type = 'check1'

{{1}}

Answer 1

date()功能对您没有任何作用。此外，个别比较通常在where条款中。

然后，您可以使用where子句中的附加条件执行您想要的操作：

SELECT *  
FROM table1 a INNER JOIN
     table2 b
     ON a.a_id = b.a_id
WHERE a.create_dt >= '2017-01-07' AND
      b.check_status = 'FAIL' AND
      b.check_type = 'check1' AND
      b.timestamp_val = (SELECT MAX(b2.timestamp_val)
                         FROM table2 b2
                         WHERE b2.a_id = b.a_id AND
                               b2.check_status = b.check_status AND
                               b2.check_type = b.check_type
                        );

Answer 2

SELECT *  
FROM table1 a
INNER JOIN table2 b
  ON a.a_id = b.a_id
    AND date(a.create_dt) >= '2017-01-07'
    AND b.check_status = 'FAIL'
    AND b.check_type = 'check1'
ORDER BY timestamp_val desc 
LIMIT 1

MYSQL：根据时间戳值从第二个表中获取最新行

2 个答案: