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How do I make a column unique and index it in a Ruby on Rails migration?
... What is the best way to do it? Also is there a way to index a column in a table?
8 Answers
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Tricks to manage the available memory in an R session
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I use the data.table package. With its := operator you can :
Add columns by reference
Modify subsets of existing columns by reference, and by group by reference
Delete columns by reference
None of these operations copy the (potentially...
Difference between filter and filter_by in SQLAlchemy
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These code examples are misleading: Declarative base table classes and instances have neither filter nor query methods; they use the session.
– Turtles Are Cute
Mar 16 '16 at 19:45
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Can you get the column names from a SqlDataReader?
...case unless I used quotes around the column name. SELECT id AS "MyId" FROM table;
– styfle
Jul 13 '13 at 0:02
sir its ...
Virtual member call in a constructor
...y are constructed, but start out as the most derived type, with the method table being for the most derived type. This means that virtual method calls always run on the most derived type.
When you combine these two facts you are left with the problem that if you make a virtual method call in a cons...
PHP: How to generate a random, unique, alphanumeric string for use in a secret link?
...unctions, then we can generate highly reliable unique strings. Here is the table showing my research data:
Update:
I created a simple Heroku app using these functions that returns the token as a JSON response. The app can be accessed at https://uniquestrings.herokuapp.com/api/token?length=15
I hope...
What do column flags mean in MySQL Workbench?
In MySQL Workbench table editor there are 7 column flags available: PK, NN, UQ, BIN, UN, ZF, AI.
3 Answers
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How can I get around MySQL Errcode 13 with SELECT INTO OUTFILE?
I am trying to dump the contents of a table to a csv file using a MySQL SELECT INTO OUTFILE statement. If I do:
13 Answers...
T-SQL: Selecting rows to delete via joins
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DELETE TableA
FROM TableA a
INNER JOIN TableB b
ON b.Bid = a.Bid
AND [my filter condition]
should work
share
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Default height for section header in UITableView
I want to set the height of the first header in my UITableView. For the other headers I want them to remain the default height. What value/constant can I put in place of "someDefaultHeight" in the code below?
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