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String concatenation in MySQL
...most DBMSs use of + or || for concatenation. It uses the CONCAT function:
SELECT CONCAT(first_name, " ", last_name) AS Name FROM test.student
As @eggyal pointed out in comments, you can enable string concatenation with the || operator in MySQL by setting the PIPES_AS_CONCAT SQL mode.
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MySQL COUNT DISTINCT
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Select
Count(Distinct user_id) As countUsers
, Count(site_id) As countVisits
, site_id As site
From cp_visits
Where ts >= DATE_SUB(NOW(), INTERVAL 1 DAY)
Group By site_id
...
How can I make Jenkins CI with Git trigger on pushes to master?
...The wiki says "when creating a job, specify URL under "Github project" and select Git specify URL under "Source Code Management". It says "This trigger only kicks Git plugin internal polling algo for every incoming event against matched repo." I think that means it pretty much does the Poll SCM like...
How to enable MySQL Query Log?
...global general_log = 1;
SET global log_output = 'table';
View the log
select * from mysql.general_log;
Disable Query logging on the database
SET global general_log = 0;
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Formatting code in Notepad++
...X -> HTML Tidy -> Tidy: Reindent XML
Remember to have the HTML code selected before you do this.
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How to make join queries using Sequelize on Node.js
...id'})
Post.find({ where: { ...}, include: [User]})
Which will give you
SELECT
`posts`.*,
`users`.`username` AS `users.username`, `users`.`email` AS `users.email`,
`users`.`password` AS `users.password`, `users`.`sex` AS `users.sex`,
`users`.`day_birth` AS `users.day_birth`,
`users`.`mo...
Pandas conditional creation of a series/dataframe column
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If you only have two choices to select from:
df['color'] = np.where(df['Set']=='Z', 'green', 'red')
For example,
import pandas as pd
import numpy as np
df = pd.DataFrame({'Type':list('ABBC'), 'Set':list('ZZXY')})
df['color'] = np.where(df['Set']=='Z', ...
Select TreeView Node on right click before displaying ContextMenu
I would like to select a WPF TreeView Node on right click, right before the ContextMenu displayed.
11 Answers
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How do MySQL indexes work?
...be faster to go through the pages one by one (in a database, this is "poor selectivity").
For a 10-page book, it makes no sense to make an index, as you may end up with a 10-page book prefixed by a 5-page index, which is just silly - just scan the 10 pages and be done with it.
The index also needs t...
How do you perform a CROSS JOIN with LINQ to SQL?
... it.
var combo = from p in people
from c in cars
select new
{
p.Name,
c.Make,
c.Model,
c.Colour
};
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