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Add a reference column migration in Rails 4
...n users table), PLUS it will also add an index on the new column.
UPDATE [For Rails 4.2]
Rails can’t be trusted to maintain referential integrity; relational databases come to our rescue here. What that means is that we can add foreign key constraints at the database level itself and ensure that...
SQL - find records from one table which don't exist in another
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yes - MySQL manual suggests that this is normal for an 'EXISTS' query
– Alnitak
Dec 17 '08 at 9:31
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How to take backup of a single table in a MySQL database?
...sername> -h <db_host> -p db_name table_name > table_name.sql
For further reference:
http://www.abbeyworkshop.com/howto/lamp/MySQL_Export_Backup/index.html
Restore
mysql -u <user_name> -p db_name
mysql> source <full_path>/table_name.sql
or in one line
mysql -u user...
MongoDB Aggregation: How to get total records count?
I have used aggregation for fetching records from mongodb.
13 Answers
13
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querySelector, wildcard element match?
...ment name match using querySelector or querySelectorAll ? I see support for wildcards in attribute queries but not for the elements themselves.
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Display open transactions in MySQL
... FULL PROCESSLIST
See: http://dev.mysql.com/doc/refman/5.1/en/thread-information.html
It will not help you, because you cannot commit a transaction from a broken connection.
What happens when a connection breaks
From the MySQL docs: http://dev.mysql.com/doc/refman/5.0/en/mysql-tips.html
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How do I add indices to MySQL tables?
...n "applied" to the data and the EXPLAIN query shows that there is no index for the field.
– Michael
Jun 9 '10 at 1:56
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MySQL order by before group by
...ents about using a subquery to accurate return this data.
MySQL does not force you to GROUP BY every column that you include in the SELECT list. As a result, if you only GROUP BY one column but return 10 columns in total, there is no guarantee that the other column values which belong to the post...
I need to generate uuid for my rails application. What are the options(gems) I have? [duplicate]
...dom.uuid #=> "1ca71cd6-08c4-4855-9381-2f41aeffe59c"
See other possible formats here.
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Custom Drawable for ProgressBar/ProgressDialog
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I used the following for creating a custom progress bar.
File res/drawable/progress_bar_states.xml declares the colors of the different states:
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:...