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How do SQL EXISTS statements work?
... criteria -- this is why it can be faster than IN. Also be aware that the SELECT clause in an EXISTS is ignored - IE:
SELECT s.*
FROM SUPPLIERS s
WHERE EXISTS (SELECT 1/0
FROM ORDERS o
WHERE o.supplier_id = s.supplier_id)
...should hit a division by zero error...
Ruby on Rails form_for select field with class
I am beating my head against the wall on this one. I want to make a simple select tag using the f.select tag but nothing I do works. I put an example below:
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What are these ^M's that keep showing up in my files in emacs?
...file, but it still let me 'git clone code.google.com/p/pytomtom' with '^m' chars?????
– Big Rich
Mar 17 '15 at 12:26
12
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How to set selected value on select using selectpicker plugin from bootstrap
I'm using the Bootstrap-Select plugin like this:
18 Answers
18
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Fastest way to determine if record exists
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SELECT TOP 1 products.id FROM products WHERE products.id = ?; will outperform all of your suggestions as it will terminate execution after it finds the first record.
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Fastest method to escape HTML tags as HTML entities?
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In normal text escaped characters are rare. It's better to call replace only when needed, if you care about max speed: if (/[<>&"]/.test(str) { ... }
– Vitaly
Oct 26 '14 at 4:22
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How to check if command line tools is installed
...ars in the Applications directory.
There are also the xcodebuild and xcode-select files in /usr/bin
I need to know if the command line tools is installed.
Is there a command for it?
What can I do to see if XCode CLT is installed and if yes to find the version installed?
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What is the difference between “INNER JOIN” and “OUTER JOIN”?
...he intersection of the two tables, i.e. the two rows they have in common.
select * from a INNER JOIN b on a.a = b.b;
select a.*, b.* from a,b where a.a = b.b;
a | b
--+--
3 | 3
4 | 4
Left outer join
A left outer join will give all rows in A, plus any common rows in B.
select * from a LEFT OUT...
Using Java to find substring of a bigger string using Regular Expression
...ch would handle nested brackets. Additionally, I believe using the indexOf(char) would be faster than indexOf(String).
– Hosam Aly
Mar 2 '09 at 11:03
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Simplest way to do a recursive self-join?
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WITH q AS
(
SELECT *
FROM mytable
WHERE ParentID IS NULL -- this condition defines the ultimate ancestors in your chain, change it as appropriate
UNION ALL
SELECT m.*
FROM mytable m
...