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[英]SQL How to select columnA and columnB where columnB has a distinct value
[英]Select Distinct values ColumnA while ColumnB = Value1 and ColumnB = Value2
這是桌子
mysql> desc tags;
+------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| content_id | int(11) | NO | | NULL | |
| name | varchar(100) | NO | | NULL | |
+------------+--------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
一些數據
mysql> select * from tags;
+----+------------+---------------+
| id | content_id | name |
+----+------------+---------------+
| 1 | 36 | banana |
| 2 | 36 | strawberry |
| 3 | 36 | orange |
| 4 | 36 | apple |
| 5 | 36 | watermelon |
| 6 | 37 | qiwi |
| 7 | 37 | apple |
| 8 | 37 | orange |
| 9 | 37 | bed |
| 10 | 38 | grape |
| 11 | 38 | apple |
+----+------------+---------------+
11 rows in set (0.00 sec)
我想要的是獲取一個唯一的content_id
s的列表,其中name
是apple並且content_id還與ORANGE綁定。
因此,在此示例中,如果我想知道哪些content_id已被“ apple”和“ orange”標記,則會導致:
+------------+
| content_id |
+------------+
| 36 |
| 37 |
+------------+
由於這些是被相應標記的僅有的兩個content_id。 最好的方法是什么?
您可以在content_id
上left join
表的content_id
,該表也具有如下名稱:
select tbl.content_id
from tags tbl
left join tags tbl2 on tbl2.content_id = tbl.content_id and tbl2.name = 'orange'
where tbl.name = 'apple' and tbl2.name is not null
group by tbl.content_id
僅返回tbl2.name is not null
指示有相應tbl2.name is not null
子句。
select content_id
from tags
where `name` in ('banana', 'orange')
group by content_id
having count(distinct `name`) >= 2
select content_id from fruits
where name in('apple','orange')
group by content_id
having COUNT(*)=2
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