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How does Rails keep track of which migrations have run for a database?
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Rails creates a table in your database called schema_migrations to keep track of which migrations have run.
The table contains a single column, version. When Rails runs a migration, it takes the leading digits in the migration's file name and inserts a row for that "version",...
What is the difference between HAVING and WHERE in SQL?
...nt(1)
From Address
Where State = 'MA'
Group By City
Gives you a table of all cities in MA and the number of addresses in each city.
This code:
select City, CNT=Count(1)
From Address
Where State = 'MA'
Group By City
Having Count(1)>5
Gives you a table of cities in MA with more than 5 address...
Git: “Not currently on any branch.” Is there an easy way to get back on a branch, while keeping the
... hash of last commit. Checkout the branch you wish to be at, and git merge _hash_
– Daniel
May 31 '12 at 13:31
BE REAL...
Remove specific commit
...hanged line 2"
1 files changed, 1 insertions(+), 1 deletions(-)
Then it all works as expected.
The second answer was very interesting. There is a feature which has not yet been officially released (though it is available in Git v1.7.2-rc2) called Revert Strategy. You can invoke git like this:
...
Age from birthdate in python
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That probably depends on your definition of "age". For all practical purposes a birthday is usually given as a date, not timezone-aware datetime (i.e., "born" is missing the details). Most people are not born at midnight sharp (so usually observe prematurely :-)), and when in a d...
What does cherry-picking a commit with Git mean?
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This is in contrast with other ways such as merge and rebase which normally apply many commits onto another branch.
Make sure you are on the branch you want to apply the commit to.
git checkout master
Execute the following:
git cherry-pick <commit-hash>
N.B.:
If you cherry-pick f...
Programmatically selecting text in an input field on iOS devices (mobile Safari)
How do you programmatically select the text of an input field on iOS devices, e.g. iPhone, iPad running mobile Safari?
10 A...
Creating a new user and password with Ansible
... parameter.
There you'll see that your password must be hashed.
- hosts: all
user: root
vars:
# created with:
# python -c 'import crypt; print crypt.crypt("This is my Password", "$1$SomeSalt$")'
password: $1$SomeSalt$UqddPX3r4kH3UL5jq5/ZI.
tasks:
- user: name=tset password={...
Why does i = i + i give me 0?
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230 + 230 = -231
-231 + -231 = 0
...in int arithmetic, since it's essentially arithmetic mod 2^32.
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What is the difference between print and puts?
... There is another thing ... extend the array class and override the to_s method. puts doesn't use the new to_s for an object of your new class while print does
– kapv89
Oct 28 '12 at 18:30
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