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SQL JOIN vs IN performance?
...king, IN and JOIN are different queries that can yield different results.
SELECT a.*
FROM a
JOIN b
ON a.col = b.col
is not the same as
SELECT a.*
FROM a
WHERE col IN
(
SELECT col
FROM b
)
, unless b.col is unique.
However, this is the syno...
LEFT OUTER JOIN in LINQ
...c.Category equals p.Category into ps
from p in ps.DefaultIfEmpty()
select new { Category = c, ProductName = p == null ? "(No products)" : p.ProductName };
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Postgresql aggregate array
...
Use array_agg: http://www.sqlfiddle.com/#!1/5099e/1
SELECT s.name, array_agg(g.Mark) as marks
FROM student s
LEFT JOIN Grade g ON g.Student_id = s.Id
GROUP BY s.Id
By the way, if you are using Postgres 9.1, you don't need to repeat the columns on SELECT to GROUP BY,...
Pandas selecting by label sometimes return Series, sometimes returns DataFrame
In Pandas, when I select a label that only has one entry in the index I get back a Series, but when I select an entry that has more then one entry I get back a data frame.
...
Maven error “Failure to transfer…”
...ed.properties).
Then go back into Eclipse, Right-click on the project and select Maven > Update Project. I selected to "Force Update of Snapshots/Releases". Click Ok and the dependencies finally resolved correctly.
shar...
Remove/Add Line Breaks after Specific String using Sublime Text
...ight Arrow > line break
The important part being Control+Command+G to select all matches.
Once you've selected the text you're looking for, you can use the provided multiple cursors to do whatever text manipulation you want.
Protip: you can manually instantiate multiple cursors by using Comman...
How to implement if-else statement in XSLT?
...oooooooooo
</h2>
XSLT 2.0 Solution
<h2>
<xsl:value-of select="if ($CreatedDate > $IDAppendedDate) then 'm' else 'd'"/>
ooooooooooooo
</h2>
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In Vim is there a way to delete without putting text in the register?
...
Any ideas on doing this selectively on only empty lines? (If I dd on an empty line it goes into the blackhole, otherwise it dds like normal).
– Jonathan Dumaine
Mar 5 '13 at 23:28
...
Xcode + remove all breakpoints
...l breakpoints.
In Xcode4 press CMD(⌘)+6, in Xcode3 press CMD(⌘)+ALT+B.
Select all breakpoints with CMD(⌘)+A and delete them, like deleting text, with backspace.
There's no step 3 :)
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How does the SQL injection from the “Bobby Tables” XKCD comic work?
..., the parenthesis makes more sense with an INSERT. Thinking backwards, the SELECT would not run anyway as the Insert of the Little Bobby Tables in the table would have already dropped the table.
– ypercubeᵀᴹ
Jan 21 '13 at 21:41
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