Question

希望有人可以提供帮助，因为我很难理解如何正确查询

我有一个Member表和一个Member_Card表。 Member_Card有一个列成员，因此该卡与成员相关联。两个表都有一个LastModifiedDate列。会员可以没有，一张或多张卡。

我需要返回其LastModifiedDate＆gt; = sinceDate（指定日期）或其卡片（如果有）LastModifiedDate＆gt; = sinceDate的所有成员。

想象一下，因为日期是2013-01-01 00:00:00。我想输出这样的东西：

[{
    "Id": "001O000000FsAs7IAF",
    "LastModifiedDate": 2013-01-01 00:00:00,
    "Member_Card": null
}, {
    "Id": "001O000000FrpIXIAZ",
    "LastModifiedDate": 2012-12-12 00:00:00,

    "Member_Card": [{
        "Id": "a00O0000002w8FGIAY",
        "Member": "001O000000FhDSoIAN",
        "LastModifiedDate": 2013-01-01 00:00:00

    }, {
        "Id": "a00O0000002uYMtIAM",
        "Member": "001O000000FhDSoIAN",
        "LastModifiedDate": 2012-12-12 00:00:00
    }]
}, {
    "Id": "001O000000FsAg7IAF",
    "LastModifiedDate": 2013-01-01 00:00:00,
    "Member_Card": [{
        "Id": "a00O0000002w8FFIAY",
        "Member": "001O000000FhDSoIAN",
        "LastModifiedDate": 2012-12-12 00:00:00
    }]
}]

第1名是匹配的LastModifiedDate没有卡的成员。第二个是具有不匹配的LastModifiedDate的成员，但他有2个关联的卡，其中一个具有匹配的LastModifiedDate。第三个是具有匹配的LastModifiedDate和卡的成员。

感谢我，我收到了以下问题：

SELECT member.*,card.* from member inner join (
SELECT distinct member.id as  mid FROM Member 
INNER JOIN Member_Card 
    ON Member_Card.Member = Member.id 
and ( Member.LastModifiedDate >= sinceDate  
    OR Member_Card.LastModifiedDate >= sinceDate ) ) a on a.mid=member.id
inner join member_card card on card.member=a.mid

哪个工作正常，但缺少会员没有任何相关卡的情况。

我尝试将一些INNER JOIN更改为LEFT JOIN但后来却忽略了日期比较： - （

你能帮我解决这个问题吗？

Answer 1

您希望将日期检查移动到内部查询的位置。

尝试类似：

SELECT member.*,card.* 
FROM member 
LEFT JOIN member_card card on card.member=member.id
WHERE member.id IN (
    SELECT DISTINCT m.id FROM Member m
        LEFT JOIN Member_Card mc ON (mc.Member = m.id)
        WHERE ( m.LastModifiedDate >= sinceDate  
        OR mc.LastModifiedDate >= sinceDate ) 
)

Answer 2

试试这个......（尚待测试）

SELECT * FROM member m1
JOIN card c1 ON c1.member = m1.id
WHERE m1.id IN (
SELECT DISTINCT m.id from member m
JOIN card c ON c.member = m.id
WHERE (c.LastModifiedDate >=sinceDate  OR m.LastModifiedDate >= sinceDate))

Answer 3

你可以这样试试，

SELECT o.status, o.date, c.name
FROM cliente c
LEFT JOIN orders o
ON c.id=o.id 
WHERE o.date = '2/1/2015'

带有WHERE子句的MySQL LEFT JOIN查询

3 个答案: