大约有 48,000 项符合查询结果（耗时：0.0310秒） [XML]
Using LIMIT within GROUP BY to get N results per group?
...
You could use GROUP_CONCAT aggregated function to get all years into a single column, grouped by id and ordered by rate:
SELECT id, GROUP_CONCAT(year ORDER BY rate DESC) grouped_year
FROM yourtable
GROUP BY id
Result:
-----------...
Replace only some groups with Regex
...
A good idea could be to encapsulate everything inside groups, no matter if need to identify them or not. That way you can use them in your replacement string. For example:
var pattern = @"(-)(\d+)(-)";
var replaced = Regex.Replace(text, pattern, "$1AA$3");
or using a MatchEv...
How to use GROUP_CONCAT in a CONCAT in MySQL
...
select id, group_concat(`Name` separator ',') as `ColumnName`
from
(
select
id,
concat(`Name`, ':', group_concat(`Value` separator ',')) as `Name`
from mytbl
group by
id,
`Name`
) tbl
group by id;
You can see...
ExpandableListView - hide indicator for groups with no children
In an ExpandableListView , is there a way to hide the group indicator for groups with no children?
13 Answers
...
Get top n records for each group of grouped results
...o do this, using UNION ALL (See SQL Fiddle with Demo). This works with two groups, if you have more than two groups, then you would need to specify the group number and add queries for each group:
(
select *
from mytable
where `group` = 1
order by age desc
LIMIT 2
)
UNION ALL
(
select ...
Relative frequencies / proportions with dplyr
Suppose I want to calculate the proportion of different values within each group. For example, using the mtcars data, how do I calculate the relative frequency of number of gears by am (automatic/manual) in one go with dplyr ?
...
SQL query to group by day
I want to list all sales, and group the sum by day.
8 Answers
8
...
SQL Server: Difference between PARTITION BY and GROUP BY
I've been using GROUP BY for all types of aggregate queries over the years. Recently, I've been reverse-engineering some code that uses PARTITION BY to perform aggregations. In reading through all the documentation I can find about PARTITION BY , it sounds a lot like GROUP BY , maybe with a ...
MongoDB SELECT COUNT GROUP BY
...be the easier way to do it using aggregate:
db.contest.aggregate([
{"$group" : {_id:"$province", count:{$sum:1}}}
])
share
|
improve this answer
|
follow
...
Can I replace groups in Java regex?
I have this code, and I want to know, if I can replace only groups (not all pattern) in Java regex.
Code:
7 Answers
...