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Why does MYSQL higher LIMIT offset slow the query down?
...30
) q
JOIN mytable t
ON t.id = q.id
See this article:
MySQL ORDER BY / LIMIT performance: late row lookups
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How to use GROUP_CONCAT in a CONCAT in MySQL
If I have a table with the following data in MySQL:
7 Answers
7
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常用Sql - 数据库(内核) - 清泛网 - 专注C/C++及内核技术
常用Sqlmysql：drop table if exists tablename;不能写成drop table tablename if exists tablename;mysql：建立索引SqlCREATE TABLE t...mysql：drop table if exists tablename;
不能写成
drop table tablename if exists tablename;
mysql：建立索引Sql
CREATE TABLE tablename (
`ID...
What's the difference between MyISAM and InnoDB? [duplicate]
...c engines you asked about (InnoDB and MyISAM) have different design goals. MySQL also has other storage engines, with their own design goals.
So, in choosing between InnoDB and MyISAM, the first step is in determining if you need the features provided by InnoDB. If not, then MyISAM is up for conside...
count(*) vs count(column-name) - which is more correct? [duplicate]
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there is a performance difference (at least in MySQL) as well (see my answer).
– nickf
Jun 9 '10 at 7:51
1
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“where 1=1” statement [duplicate]
I saw some people use a statement to query a table in a MySQL database like the following:
10 Answers
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Kill a postgresql session/connection
...g the database.
def drop_database(config)
case config['adapter']
when /mysql/
ActiveRecord::Base.establish_connection(config)
ActiveRecord::Base.connection.drop_database config['database']
when /sqlite/
require 'pathname'
path = Pathname.new(config['database'])
file = path....
How does this giant regex work?
...pecially FTP, although should be using sftp or ftps.
If you control your MySQL server make sure your web application's MySQL user account is not root, and make sure you remove MySQL FILE privileges from the account. You should also go a step further and do a chmod 500 -R /path/to/web/root and d...
Why does “_” (underscore) match “-” (hyphen)?
...cluding zero characters).
(From section 3.3.4.7. Pattern Matching in the MySQL documentation.)
If you want to use the underscore in like as a literal, you have to escape it:
select * from a where name like '%taz\_manual%.pdf%';
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PostgreSQL Autoincrement
I'm switching from MySQL to PostgreSQL and was wondering how I can do autoincrement values. I saw in the PostgreSQL docs a datatype "serial", but I get syntax errors when using it (in v8.0).
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