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Ruby: How to get the first character of a string
How can I get the first character in a string using Ruby?
13 Answers
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Rails raw SQL example
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You can do this:
sql = "Select * from ... your sql query here"
records_array = ActiveRecord::Base.connection.execute(sql)
records_array would then be the result of your sql query in an array which you can iterate through.
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Removing an item from a select box
How do I remove items from, or add items to, a select box? I'm running jQuery, should that make the task easier. Below is an example select box.
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Check if value exists in Postgres array
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Simpler with the ANY construct:
SELECT value_variable = ANY ('{1,2,3}'::int[])
The right operand of ANY (between parentheses) can either be a set (result of a subquery, for instance) or an array. There are several ways to use it:
SQLAlchemy: how to filt...
MySQL Great Circle Distance (Haversine formula)
...ults. To search by kilometers instead of miles, replace 3959 with 6371.
SELECT id, ( 3959 * acos( cos( radians(37) ) * cos( radians( lat ) )
* cos( radians( lng ) - radians(-122) ) + sin( radians(37) ) * sin(radians(lat)) ) ) AS distance
FROM markers
HAVING distance < 25
ORDER BY distance ...
How to find the size of localStorage
...ntil DevTools are opened)
Opera 12.15 ~4212ms /3.55Mb (this is when 5Mb is selected, but Opera asks nicely if we want increase the amount of lS, unfortunately it crashes if test conducted a few times in a row)
Win 8 (Under Parallels 8)
IE10 ~7850ms /9.54Mb
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Writing a compiler in its own language
...s, specifically escape sequences. You will write code to convert \n to the character with the decimal code 10 (and \r to 13, etc).
After that compiler is ready, you will start to reimplement it in C. This process is called "bootstrapping".
The string parsing code will become:
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if (c == 92) { /...
Get current AUTO_INCREMENT value for any table
...'TableName' ;
You can get exactly this information by using this query:
SELECT `AUTO_INCREMENT`
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_SCHEMA = 'DatabaseName'
AND TABLE_NAME = 'TableName';
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What does it mean by select 1 from table?
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SELECT 1 FROM TABLE_NAME means, "Return 1 from the table". It is pretty unremarkable on its own, so normally it will be used with WHERE and often EXISTS (as @gbn notes, this is not necessarily best practice, it is, however, c...
Check if option is selected with jQuery, if not select a default
Using jQuery, how do you check if there is an option selected in a select menu, and if not, assign one of the options as selected.
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