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Changing column names of a data frame
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Try setnames() in the data.table package. Use something like setnames(DT,"b","B") or setnames(DT,c("a","E"),c("A","F"))
– dwstu
Aug 11 '14 at 17:23
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sql primary key and index
...ou may reach the desired optimization for a query.
For example you have a table with many columns but you are only querying ID, Name and Address columns. Taking ID as the primary key, we can create the following index that is built on ID but includes Name and Address columns.
CREATE NONCLUSTERED I...
PostgreSQL: How to pass parameters from command line?
...'"
and then refer to the variables in sql as :v1, :v2 etc
select * from table_1 where id = :v1;
Please pay attention on how we pass string/date value using two quotes " '...' "
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ActiveRecord OR query
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Use ARel
t = Post.arel_table
results = Post.where(
t[:author].eq("Someone").
or(t[:title].matches("%something%"))
)
The resulting SQL:
ree-1.8.7-2010.02 > puts Post.where(t[:author].eq("Someone").or(t[:title].matches("%something%"))).to_...
How to use ng-repeat without an html element
... on tbody? (AFAIK, it is okay to have multiple <tbody>s in a single table.)
<tbody ng-repeat="row in array">
<tr ng-repeat="item in row">
<td>{{item}}</td>
</tr>
</tbody>
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How big can a MySQL database get before performance starts to degrade
...data. The most important scalability factor is RAM. If the indexes of your tables fit into memory and your queries are highly optimized, you can serve a reasonable amount of requests with a average machine.
The number of records do matter, depending of how your tables look like. It's a difference ...
Database Structure for Tree Data Structure
... Considering a structure as in number one topic (organizational structured table (not employee structured) with ParentId referenced in the same table), I need to set who is the boss of a certain area. I will assign all the employees of that specific area directly to it. Where would you put the boss ...
CSS to make HTML page footer stay at bottom of the page with a minimum height, but not overlap the p
...w are 4 different methods of mine:
In each example the texts are freely-editable to illustrate how the content would render in different scenarios.
1) Flexbox
body{ height:100vh; margin:0; }
header{ min-height:50px; background:lightcyan; }
footer{ min-height:50px; background:PapayaWhip; }
/* ...
insert multiple rows via a php array into mysql
I'm passing a large dataset into a MySQL table via PHP using insert commands and I'm wondering if its possible to insert approximately 1000 rows at a time via a query other than appending each value on the end of a mile long string and then executing it. I am using the CodeIgniter framework so its f...
Is there a way to disable initial sorting for jquery DataTables?
I'm using the jquery DataTables plugin. From their documentation:
4 Answers
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