[英]In a mysql UNION can I exclude rows from the left part in the right part
I have a table where I store records for either a person or a group.我有一张表,用于存储个人或组的记录。
|id|entity_id|person_id|group_id|
|1 |000000001|999999999|NULL |
|2 |000000001|NULL |88888888|
|3 |000000002|999999999|NULL |
|4 |000000003|NULL |88888888|
How can I get all the records for person_id 999999999 and group_id 88888888, but the latter only when I do not have a record with entity_id 000000001 for person_id 999999999如何获取 person_id 999999999 和 group_id 88888888 的所有记录,但后者仅在我没有 person_id 999999999 的 entity_id 000000001 的记录时
So my result should be所以我的结果应该是
|id|entity_id|person_id|group_id|
|1 |000000001|999999999|NULL |
|3 |000000002|999999999|NULL |
|4 |000000003|NULL |88888888|
I am hoping this is possible in one query, but UNION, EXCEPT do not seem to do the trick.我希望这在一个查询中是可能的,但是 UNION, EXCEPT 似乎并不能解决问题。
I was trying something like我正在尝试类似的东西
SELECT *
from myTable m1
WHERE NOT IS NULL person_id
UNION ALL
SELECT *
from myTable m2
WHERE NOT IS NULL group_id
EXCEPT (SELECT entity_id FROM m1)
but apparently mysql doesn't support EXCEPT但显然 mysql 不支持 EXCEPT
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