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Best way to select random rows PostgreSQL
I want a random selection of rows in PostgreSQL, I tried this:
12 Answers
12
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How do you connect to multiple MySQL databases on a single webpage?
...d);
$dbh2 = mysql_connect($hostname, $username, $password, true);
mysql_select_db('database1', $dbh1);
mysql_select_db('database2', $dbh2);
Then to query database 1 pass the first link identifier:
mysql_query('select * from tablename', $dbh1);
and for database 2 pass the second:
mysql_query...
Select first row in each GROUP BY group?
As the title suggests, I'd like to select the first row of each set of rows grouped with a GROUP BY .
17 Answers
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Mysql command not found in OS X 10.7
I cant get my mysql to start on os x 10.7. It is located in /usr/local/mysql/bin/mysql
14 Answers
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What makes a SQL statement sargable?
...non-sargable is to include a field inside a function in the where clause:
SELECT ... FROM ...
WHERE Year(myDate) = 2008
The SQL optimizer can't use an index on myDate, even if one exists. It will literally have to evaluate this function for every row of the table. Much better to use:
WHERE myDat...
Accessing inactive union member and undefined behavior?
I was under the impression that accessing a union member other than the last one set is UB, but I can't seem to find a solid reference (other than answers claiming it's UB but without any support from the standard).
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LINGO使用指南 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...型都都要在该窗口内编码实现。下面举两个例子。
例1.1 如何在LINGO中求解如下的LP问题：
在模型窗口中输入如下代码：
min=2*x1+3*x2;
x1+x2>=350;
x1>=100;
2*x1+x2<=600;
然后点击工具条上的按钮 即可。
例1.2 使用LINGO软件计算6个...
How to take MySQL database backup using MySQL Workbench?
...ble) within Server Administration.
Steps to Create New Server Instance:
Select New Server Instance option within Server Administrator.
Provide connection details.
After creating new server instance , it will be available in Server Administration list. Double click on Server instance you have cr...
MySQL: determine which database is selected?
After calling mysql_select_db to grab a database, is there any way to later output the name of the database that is currently selected? This seems very basic but I couldn't find anything on php.net or stackoverflow (all results are for "no database selected").
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SQL Server query to find all permissions/access for all users in a database
...s the user/role has on an object. Examples could include CONNECT, EXECUTE, SELECT
DELETE, INSERT, ALTER, CONTROL, TAKE OWNERSHIP, VIEW DEFINITION, etc.
This value may not be populated for all roles. Some built in roles have implicit permission
d...