mysql - mysql 中的条件连接表

Question

我有两张 table 。我想要列出这些表中 guest_id 1 允许和不允许的所有事件。

第一个表

activity_name_id | activity_name |

    1                 Entry

    2                 Exit

    3                 Break

第二个表

allowed_guest_id | allowed_activity_name_id |
    1                 1
    2                 1
    1                 3
    2                 4

现在我想要结果

activity_name_id | activity_name |allowed_guest_id | allowed_activity_name_id |

    1                 Entry                1                 1

    2                 Exit                 null              2

    3                 Break                1                 3

我已经尝试过了。但它只返回两行。第一个和最后一个。

select * from table_activity_name
    left join table_allowed_activity 
    on activity_name_id = allowed_activity_name_id
        where allowed_activity_guest_id = 1;

Answer 1

试试这个

select ta.activity_name_id, ta.activity_name, tal.allowed_guest_id, tal.allowed_activity_name_id from table_activity_name as ta
left join table_allowed_activity  as tal
on ta.activity_name_id = tal.allowed_activity_name_id
and tal.allowed_activity_guest_id = 1;

或IN操作

select ta.activity_name_id, ta.activity_name, tal.allowed_guest_id, tal.allowed_activity_name_id from table_activity_name as ta
left join table_allowed_activity  as tal
on ta.activity_name_id = tal.allowed_activity_name_id
and tal.allowed_activity_guest_id in (1,2);