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MySQL: Transactions vs Locking Tables
I'm a bit confused with transactions vs locking tables to ensure database integrity and make sure a SELECT and UPDATE remain in sync and no other connection interferes with it. I need to:
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I need to generate uuid for my rails application. What are the options(gems) I have? [duplicate]
... the column.
Example in Rails 3 migration
execute <<-SQL
CREATE TABLE some_items (id uuid PRIMARY KEY DEFAULT uuid_generate_v1());
SQL
Might be a better way to do this in Rails 4.
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Expand/collapse section in UITableView in iOS
Could somebody tell me the way to perform UITableView expandable/collapsible animations in sections of UITableView as below?
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How do I replace NA values with zeros in an R dataframe?
...the complete results.
If you are struggling with massive dataframes, data.table is the fastest option of all: 40% faster than the standard Base R approach. It also modifies the data in place, effectively allowing you to work with nearly twice as much of the data at once.
A clustering of other he...
How can I get Express to output nicely formatted HTML?
...:
foo.jade
h1 MyTitle
p
a(class='button', href='/users/') show users
table
thead
tr
th Name
th Email
tbody
- var items = [{name:'Foo',email:'foo@bar'}, {name:'Bar',email:'bar@bar'}]
- each item in items
tr
td= item.name
td= item.email
now you...
Should I index a bit field in SQL Server?
...k for a set of rows, SQL uses the index to find the rows more quickly than table scanning (looking at every row).
SQL has clustered and non-clustered indexes. My understanding of clustered indexes is that they group similar index values into the same page. This way when you ask for all the rows m...
Advantage of switch over if-else statement
...tree (saves compares and jumps in the average case) or simply build a jump-table (works without compares at all).
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Rails 4 LIKE query - ActiveRecord adds quotes
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def self.search(query, page=1)
query = "%#{query}%"
name_match = arel_table[:name].matches(query)
postal_match = arel_table[:postal_code].matches(query)
where(name_match.or(postal_match)).page(page).per_page(5)
end
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Query for documents where array size is greater than 1
... @Tobia my first use was $exists only but it actually use whole table scan so very slow. db.test.find({"name":"abc","d.5":{$exists:true},"d.6":{$exists:true}}) "nReturned" : 46525, "executionTimeMillis" : 167289, "totalKeysExamined" : 10990840, "totalDocsExamined" : 10990840, ...
postgresql - sql - count of `true` values
In the above table, if I do :
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