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Count number of rows within each group
... have a dataframe and I would like to count the number of rows within each group. I reguarly use the aggregate function to sum data as follows:
...
Get statistics for each group (such as count, mean, etc) using pandas GroupBy?
I have a data frame df and I use several columns from it to groupby :
7 Answers
7
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Find most frequent value in SQL column
... COUNT(`column`) AS `value_occurrence`
FROM `my_table`
GROUP BY `column`
ORDER BY `value_occurrence` DESC
LIMIT 1;
Replace column and my_table. Increase 1 if you want to see the N most common values of the column.
...
Regular Expression to get a string between parentheses in Javascript
...e a set of escaped (with \) parentheses (that match the parentheses) and a group of regular parentheses that create your capturing group:
var regExp = /\(([^)]+)\)/;
var matches = regExp.exec("I expect five hundred dollars ($500).");
//matches[1] contains the value between the parentheses
...
Find all records which have a count of an association greater than zero
... vacancy.
UPDATE:
As pointed out by @mackskatz in the comment, without a group clause, the code above will return duplicate projects for projects with more than one vacancies. To remove the duplicates, use
Project.joins(:vacancies).group('projects.id')
UPDATE:
As pointed out by @Tolsee, you c...
SQL Group By with an Order By
...rder by the alias:
SELECT COUNT(id) AS theCount, `Tag` from `images-tags`
GROUP BY `Tag`
ORDER BY theCount DESC
LIMIT 20
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Split List into Sublists with LINQ
...source
.Select((x, i) => new { Index = i, Value = x })
.GroupBy(x => x.Index / 3)
.Select(x => x.Select(v => v.Value).ToList())
.ToList();
}
The idea is to first group the elements by indexes. Dividing by three has the effect of grouping them into group...
how to exclude null values in array_agg like in string_agg using postgres?
...g.canonical = 'N' THEN g.users ELSE NULL END) non_canonical_users
FROM groups g
GROUP BY g.id
) s
Or, simpler and may be cheaper, using array_to_string which eliminates nulls:
SELECT
g.id,
array_to_string(
array_agg(CASE WHEN g.canonical = 'Y' THEN g.users ELSE NULL END)
...
MySQL: Invalid use of group function
...fference is: the WHERE clause filters which rows MySQL selects. Then MySQL groups the rows together and aggregates the numbers for your COUNT function.
HAVING is like WHERE, only it happens after the COUNT value has been computed, so it'll work as you expect. Rewrite your subquery as:
( ...
How to calculate percentage with a SQL statement
...(Count(Grade)* 100 / (Select Count(*) From MyTable)) as Score
From MyTable
Group By Grade
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