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Compare two data.frames to find the rows in data.frame 1 that are not present in data.frame 2
...ata.frame(a = 1:3, b=letters[1:3])
require(sqldf)
a1NotIna2 <- sqldf('SELECT * FROM a1 EXCEPT SELECT * FROM a2')
And the rows which are in both data frames:
a1Ina2 <- sqldf('SELECT * FROM a1 INTERSECT SELECT * FROM a2')
The new version of dplyr has a function, anti_join, for exactly the...
Unable to login to SQL Server + SQL Server Authentication + Error: 18456
...tion.
You can access this by
Right click on instance (IE SQLServer2008)
Select "Properties"
Select "Security" option
Change "Server authentication" to "SQL Server and Windows Authentication mode"
Restart the SQLServer service
Right click on instance
Click "Restart"
...
Find difference between timestamps in seconds in PostgreSQL
...
Try:
SELECT EXTRACT(EPOCH FROM (timestamp_B - timestamp_A))
FROM TableA
Details here: EXTRACT.
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MySQL stored procedure vs function, which would I use when?
...d procedures with ordinary SQL, whilst with stored function you can.
e.g. SELECT get_foo(myColumn) FROM mytable is not valid if get_foo() is a procedure, but you can do that if get_foo() is a function. The price is that functions have more limitations than a procedure.
...
c# datatable to csv
...s = dt.Columns.Cast<DataColumn>().
Select(column => column.ColumnName).
ToArray();
sb.AppendLine(string.Join(",", columnNames));
foreach (DataRow row in dt.Rows)
{
string[] fields = row.ItemArray.Select(field => fie...
PostgreSQL, checking date relative to “today”
...
select * from mytable where mydate > now() - interval '1 year';
If you only care about the date and not the time, substitute current_date for now()
...
Simple way to copy or clone a DataRow?
...lone();
// Note: .Copy(), by contrast, would clone the data rows also.
// Select the data row to clone, e.g. the 2nd one:
var row = table.Rows[1];
// Import the data row of interest into the aux. table.
// This creates a *shallow clone* of it.
// Note: If you'll be *reusing* the aux. table for sin...
开源MQTT网关：EMQX vs Mosquitto - 创客硬件开发 - 清泛IT社区，为创新赋能！
引言物联网开发者需要为自己的物联网项目选择合适的 MQTT 消息产品或服务，从而构建可靠高效的基础数据层，保障上层物联网业务。目前市面上有很多开源的 MQTT 产品，在性能功能等方面各有优点。本文将选取目前最为流行的...
How to change tab size on GitHub?
... by changing the blob segment with an edit segment and use the dropdown to select your prefered tab size.
Standard view: https://github.com/moroshko/mmSelect/blob/master/mm_select.js
Ace view: https://github.com/moroshko/mmSelect/edit/master/mm_select.js
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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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