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Aggregate / summarize multiple variables per group (e.g. sum, mean)
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Using the data.table package, which is fast (useful for larger datasets)
https://github.com/Rdatatable/data.table/wiki
library(data.table)
df2 <- setDT(df1)[, lapply(.SD, sum), by=.(year, month), .SDcols=c("x1","x2")]
setDF(df2) # con...
What are the pros and cons to keeping SQL in Stored Procs versus Code [closed]
... the SQL inline in C# and calling to the SQL Server DB. So I'm trying to establish which, for this particular project, would be best.
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Tactics for using PHP in a high-load site
...lize your schemas. This means that rather than to have multiple relational tables, you should instead opt to have one big table. In general, joins are a waste of precious DB resources because doing multiple prepares and collation burns disk I/O's. Avoid them when you can.
The trade-off here is ...
python pandas remove duplicate columns
...d, the problem is probably with the duplicate column titles.
For a sample table file 'dummy.csv' I made up:
Time H1 N2 Time N2 Time Relative
3 13 13 3 13 0
1 15 15 1 15 14
14 19 19 14 19 14
19 5 5 19 5 1
using read_table gives unique columns and works properly...
What are the complexity guarantees of the standard containers?
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I'm not aware of anything like a single table that lets you compare all of them in at one glance (I'm not sure such a table would even be feasible).
Of course the ISO standard document enumerates the complexity requirements in detail, sometimes in various rather r...
Repeater, ListView, DataList, DataGrid, GridView … Which to choose?
...t you trying to achieve
Gridview - Limited in design, works like an html table. More in built functionality like edit/update, page, sort. Lots of overhead.
DataGrid - Old version of the Gridview. A gridview is a super datagrid.
Datalist - more customisable version of the Gridview. Also has some o...
SELECT DISTINCT on one column
...R() OVER (PARTITION BY PRODUCT ORDER BY ID) AS RowNumber
FROM MyTable
WHERE SKU LIKE 'FOO%') AS a
WHERE a.RowNumber = 1
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Boolean Field in Oracle
Yesterday I wanted to add a boolean field to an Oracle table. However, there isn't actually a boolean data type in Oracle. Does anyone here know the best way to simulate a boolean? Googling the subject discovered several approaches
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How to count instances of character in SQL Column
...LESCE(NULLIF(LEN(@StringToFind), 0), 1) --protect division from zero
FROM [Table To Search]
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Difference between FOR and AFTER triggers?
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There is no difference, they do the same thing.
CREATE TRIGGER trgTable on dbo.Table FOR INSERT,UPDATE,DELETE
Is the same as
CREATE TRIGGER trgTable on dbo.Table AFTER INSERT,UPDATE,DELETE
An INSTEAD OF trigger is different, and fires before and instead of the insert and can be used on...