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How to select the rows with maximum values in each group with dplyr? [duplicate]
I would like to select a row with maximum value in each group with dplyr.
6 Answers
6
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How to update column with null value
...Hello');
UPDATE your_table
SET your_column = NULL
WHERE some_id = 1;
SELECT * FROM your_table WHERE your_column IS NULL;
+---------+-------------+
| some_id | your_column |
+---------+-------------+
| 1 | NULL |
+---------+-------------+
1 row in set (0.00 sec)
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How to implement classic sorting algorithms in modern C++?
...ed and hybrid amalgamation of more elementary sorting algorithms , such as selection sort, insertion sort, quick sort, merge sort, or heap sort.
...
Eclipse: How do i refresh an entire workspace? F5 doesn't do it
...le->Refresh , it doesn't really refresh anything (perhaps the currently selected project). How do I get eclipse to refresh all of the projects?
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Is it possible to use Java 8 for Android development?
...ce
Click on the Android SDK Manager button which is located on the toolbar
Select Android SDK Build tools Rev. 19.1 and Android Support Library only. Un-select everything else and install these two packages.
If everything goes well, ADT will be up and running.
The installation of the following to...
How to Get True Size of MySQL Database?
... would like to know how much space does my MySQL database use, in order to select a web host.
I found the command SHOW TABLE STATUS LIKE 'table_name' so when I do the query, I get something like this:
...
PostgreSQL: Drop PostgreSQL database through command line [closed]
...rrently taking place against your database, including all idle processes.
SELECT * FROM pg_stat_activity WHERE datname='database name';
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What's the difference between NOT EXISTS vs. NOT IN vs. LEFT JOIN WHERE IS NULL?
... using Standard SQL.
An obvious omission is the equivalent using EXCEPT:
SELECT a FROM table1
EXCEPT
SELECT a FROM table2
Note in Oracle you need to use the MINUS operator (arguably a better name):
SELECT a FROM table1
MINUS
SELECT a FROM table2
Speaking of proprietary syntax, there may also ...
Select values from XML field in SQL Server 2008
...
Given that the XML field is named 'xmlField'...
SELECT
[xmlField].value('(/person//firstName/node())[1]', 'nvarchar(max)') as FirstName,
[xmlField].value('(/person//lastName/node())[1]', 'nvarchar(max)') as LastName
FROM [myTable]
...
SQL “select where not in subquery” returns no results
...MySQL
There are three ways to do such a query:
LEFT JOIN / IS NULL:
SELECT *
FROM common
LEFT JOIN
table1 t1
ON t1.common_id = common.common_id
WHERE t1.common_id IS NULL
NOT EXISTS:
SELECT *
FROM common
WHERE NOT EXISTS
(
SELECT NULL
FROM ...