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How do I extract a sub-hash from a hash?
...e same:
h1 = {:a => :A, :b => :B, :c => :C, :d => :D}
h2 = h1.select {|key, value| [:b, :d, :e, :f].include?(key) } # => {:b=>:B, :d=>:D}
h1 = Hash[h1.to_a - h2.to_a] # => {:a=>:A, :c=>:C}
And if you want to patch that into the Hash class:
class Hash
def extract...
How to avoid mysql 'Deadlock found when trying to get lock; try restarting transaction'
...now() - INTERVAL 900 SECOND
To
DELETE FROM onlineusers
WHERE id IN (
SELECT id FROM onlineusers
WHERE datetime <= now() - INTERVAL 900 SECOND
ORDER BY id
) u;
Another thing to keep in mind is that mysql documentation suggest that in case of a deadlock the client should retry autom...
How to get all columns' names for all the tables in MySQL?
...
select * from information_schema.columns
where table_schema = 'your_db'
order by table_name,ordinal_position
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impro...
Postgres NOT in array
...
SELECT COUNT(*) FROM "messages" WHERE NOT (3 = ANY (recipient_ids))
You can always negate WHERE (condition) with WHERE NOT (condition)
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Selecting with complex criteria from pandas.DataFrame
...se pandas it has some built in functions for comparison. So if you want to select values of "A" that are met by the conditions of "B" and "C" (assuming you want back a DataFrame pandas object)
df[['A']][df.B.gt(50) & df.C.ne(900)]
df[['A']] will give you back column A in DataFrame format.
pan...
Android Studio Editor Font Sizing
...
In MacBook Android Studio ->
Select Preferences... ->
Click on Save As.. ->Give any name -> OK -> then select Scheme -> and you given name every option Editable
s...
What does collation mean?
... is a correctly ordered list:
Namibia
número
ñandú
ñú
obra
ojo
By selecting the correct collation, you get all this done for you, automatically :-)
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Xcode - How to fix 'NSUnknownKeyException', reason: … this class is not key value coding-compliant f
...ng from "File's Owner" under "Place Holders" to "view" under "Objects" and selecting the view outlet.
– Nirma
Aug 11 '11 at 14:49
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Why there is no ForEach extension method on IEnumerable?
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Couldn't you just use Select instead of your Apply method? It seems to me that applying an action to each element and yielding it is exactly what Select does. E.g. numbers.Select(n => n*2);
– rasmusvhansen
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Copying data from one SQLite database to another
...rt Into commands for the tables you want to transfer.
INSERT INTO X.TABLE SELECT * FROM Y.TABLE;
Or, if the columns are not matched up in order:
INSERT INTO X.TABLE(fieldname1, fieldname2) SELECT fieldname1, fieldname2 FROM Y.TABLE;
...