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Purge or recreate a Ruby on Rails database
...test:prepare for testing, or else you'll get an error like: Could not find table 'things' (ActiveRecord::StatementInvalid)
– s2t2
Feb 17 '13 at 1:49
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Two single-column indexes vs one two-column index in MySQL?
...a single composite index can speed up several kinds of queries on the same table." - Multiple-Column Indexes
– AlikElzin-kilaka
Sep 9 '18 at 4:46
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UITableView - change section header color
How can I change color of a section header in UITableView?
31 Answers
31
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Why is XOR the default way to combine hashes?
... uniform probability distributions.
This can be seen by writing out truth tables:
a | b | a AND b
---+---+--------
0 | 0 | 0
0 | 1 | 0
1 | 0 | 0
1 | 1 | 1
a | b | a OR b
---+---+--------
0 | 0 | 0
0 | 1 | 1
1 | 0 | 1
1 | 1 | 1
a | b | a XOR b
---+---+--------
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UITableView is starting with an offset in iOS 7
I have dragged a plain jane UITableView onto a UIViewController in iOS 7.
20 Answers
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Introducing FOREIGN KEY constraint may cause cycles or multiple cascade paths - why?
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I had a table that had a circular relationship with others and i was getting the same error. Turns out it is about the foreign key which was not nullable. If key is not nullable related object must be deleted and circular relations d...
UITableViewCell subview disappears when cell is selected
I'm implementing a color-chooser table view where the user can select amongst, say, 10 colors (depends on the product). The user can also select other options (like hard drive capacity, ...).
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log4j logging hierarchy order
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This table might be helpful for you:
Going down the first column, you will see how the log works in each level. i.e for WARN, (FATAL, ERROR and WARN) will be visible. For OFF, nothing will be visible.
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Rake just one migration
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To expand on what Ryan says, if the table has been dropped from the database outside of Rails, rake db:migrate:up VERSION=my_version may do nothing, because the schema_migrations table still says it is has been run. In the same situation rake db:migrate:redo VE...
Best way to clear a PHP array's values
...hing more powerful use unset since it also will clear $foo from the symbol table, if you need the array later on just instantiate it again.
unset($foo); // $foo is gone
$foo = array(); // $foo is here again
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