[英]Create subquery in Laravel - Query builder
I try to create a sub query. 我尝试创建一个子查询。 For now, my two queries are : 现在,我的两个查询是:
select `key` from messages group by `key`;
and 和
select * from messages where `key` = 'KEY_RECUP_AU_DESSUS' order by created_at DESC LIMIT 1;
The aim is to highlight my table messages
all elements grouped by key and keeping the last element ( created_at desc) 目的是突出显示表messages
按键分组的所有元素,并保留最后一个元素(created_at desc)
Thank you 谢谢
Something like this should work: 这样的事情应该起作用:
$data = DB::table('messages')->whereIn('key',function($q) {
$q->select('key')->from('messages')->groupBy('key');
})->latest()->take(1)->get();
You can do this with two different ways. 您可以使用两种不同的方法来完成此操作。
Query Builder: 查询生成器:
DB::table('messages AS a')
->leftJoin('messages AS b', function($join) {
$join->on('a.created_at', '<', 'b.created_at');
$join->on('a.key', '=', 'b.key');
})
->groupBy(['a.key', 'a.message', 'a.created_at'])
->havingRaw('COUNT(b.key) < 1')
->select(['a.key', 'a.message', 'a.created_at'])
->get();
Another way with PARTITION BY PARTITION BY的另一种方式
SELECT
key,
message,
created_at
FROM (
SELECT
key,
message,
created_at,
rank() OVER (PARTITION BY key ORDER BY created_at DESC) AS rank
FROM
messages
) AS foo WHERE foo.rank = 1;
if we assume you have table like this. 如果我们假设您有这样的表。
postgres=# select * from messages;
id | key | message | created_at
----+---------+------------------------+----------------------------
1 | contact | send from contact page | 2015-10-31 19:45:16.850698
2 | contact | contact page message | 2015-10-31 19:45:34.417231
3 | product | product 1 | 2015-10-31 19:45:44.49584
4 | product | product 2 | 2015-10-31 19:45:46.856691
5 | contact | hello it is me | 2015-10-31 18:45:35.801967
6 | about | who are you | 2015-10-31 19:46:04.123369
7 | product | product 3 | 2015-10-31 19:46:12.414364
8 | about | hi guys | 2015-10-31 19:46:18.23442
(8 rows)
The result will be like this with two different query 结果将是这样,带有两个不同的查询
postgres=# select key, message, created_at from (select key, message, created_at, rank() over (partition by key order by created_at desc) as rank from messages) foo where rank = 1;
key | message | created_at
---------+----------------------+----------------------------
about | hi guys | 2015-10-31 19:46:18.23442
contact | contact page message | 2015-10-31 19:45:34.417231
product | product 3 | 2015-10-31 19:46:12.414364
(3 rows)
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.