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How to reshape data from long to wide format
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Another option if performance is a concern is to use data.table's extension of reshape2's melt & dcast functions
(Reference: Efficient reshaping using data.tables)
library(data.table)
setDT(dat1)
dcast(dat1, name ~ numbers, value.var = "value")
# name 1 ...
What is the advantage to using bloom filters?
...esenting sets, such as
self-balancing binary search trees,
tries, hash tables, or simple arrays
or linked lists of the entries. Most
of these require storing at least the
data items themselves, which can
require anywhere from a small number
of bits, for small integers, to an
arbitrar...
How do I delete from multiple tables using INNER JOIN in SQL server
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You can take advantage of the "deleted" pseudo table in this example. Something like:
begin transaction;
declare @deletedIds table ( id int );
delete from t1
output deleted.id into @deletedIds
from table1 as t1
inner join table2 as t2
on t2.id = t...
What's the difference between identifying and non-identifying relationships?
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An identifying relationship is when the existence of a row in a child table depends on a row in a parent table. This may be confusing because it's common practice these days to create a pseudokey for a child table, but not make the foreign key to the parent part of the child's primary key. Fo...
How can I make Bootstrap columns all the same height?
...margin-bottom: -99999px;
padding-bottom: 99999px;
}
Solution 2 using table
Demo
.row {
display: table;
}
[class*="col-"] {
float: none;
display: table-cell;
vertical-align: top;
}
Solution 3 using flex added August 2015. Comments posted before this don't apply to this sol...
php is null or empty?
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As is shown in the following table, empty($foo) is equivalent to $foo==null and is_null($foo) has the same function of $foo===null. The table also shows some tricky values regarding the null comparison. (ϕ denotes an uninitialized variables. )
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Cannot change column used in a foreign key constraint
I got this error when i was trying to alter my table.
3 Answers
3
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Form inside a table
I'm including some forms inside a HTML table to add new rows and update current rows. The problem that I'm getting is that when I inspect the forms in my dev tools, I see that the form elements are closed immediately after opening (inputs, etc are not included within the form).
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MySQL remove all whitespaces from the entire column
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To replace all spaces :
UPDATE `table` SET `col_name` = REPLACE(`col_name`, ' ', '')
To remove all tabs characters :
UPDATE `table` SET `col_name` = REPLACE(`col_name`, '\t', '' )
To remove all new line characters :
UPDATE `table` SET `col_name` = REP...
Naming of ID columns in database tables
I was wondering peoples opinions on the naming of ID columns in database tables.
24 Answers
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