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Is it possible to roll back CREATE TABLE and ALTER TABLE statements in major SQL databases?
...es. Also, not all situations are quite handled- for example, if you try to select from table foo while another transaction is dropping it and creating a replacement table foo, then the blocked transaction will finally receive an error rather than finding the new foo table. (Edit: this was fixed in o...
How to change the CHARACTER SET (and COLLATION) throughout a database?
...re schema to utf8. Hope this helps!
-- Change DATABASE Default Collation
SELECT DISTINCT concat('ALTER DATABASE `', TABLE_SCHEMA, '` CHARACTER SET utf8 COLLATE utf8_unicode_ci;')
from information_schema.tables
where TABLE_SCHEMA like 'database_name';
-- Change TABLE Collation / Char Set
SELECT...
How do I UPDATE from a SELECT in SQL Server?
... SQL Server , it is possible to insert rows into a table with an INSERT.. SELECT statement:
35 Answers
...
mysql query order by multiple items
...
SELECT some_cols
FROM prefix_users
WHERE (some conditions)
ORDER BY pic_set DESC, last_activity;
share
|
improve this answ...
creating a random number using MYSQL
I would like to know is there a way to select randomly generated number between 100 and 500 along with a select query.
6 A...
What is SQL injection? [duplicate]
...ue for any language), which might be used to handle a user login.
$sql = "SELECT FROM users WHERE username='".$_GET['username']."' AND password='".$_GET['password']."'";
The harm is done when the user enters something like
administrator'; --
... for the username. Without proper encoding the...
SQL - using alias in Group By
... following order:
FROM clause
WHERE clause
GROUP BY clause
HAVING clause
SELECT clause
ORDER BY clause
For most relational database systems, this order explains which names (columns or aliases) are valid because they must have been introduced in a previous step.
So in Oracle and SQL Server, you...
How to implement LIMIT with SQL Server?
...05, you can do this...
USE AdventureWorks;
GO
WITH OrderedOrders AS
(
SELECT SalesOrderID, OrderDate,
ROW_NUMBER() OVER (ORDER BY OrderDate) AS 'RowNumber'
FROM Sales.SalesOrderHeader
)
SELECT *
FROM OrderedOrders
WHERE RowNumber BETWEEN 10 AND 20;
or something like this for 2000 ...
BIO与NIO、AIO的区别(这个容易理解) - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...给OS处理，需要将数据缓冲区地址和大小传给OS(银行卡和密码)，OS需要支持异步IO操作API）；
阻塞 ： ATM排队取款，你只能等待（使用阻塞IO时，Java调用会一直阻塞到读写完成才返回）；
非阻塞 ： 柜台取款，取个号，然后坐在...
PDOException “could not find driver”
...your server.
In Ubuntu/Debian you check for the package with:
dpkg --get-selections | grep php | grep mysql
Install the php5-mysql package if you do not have it.
In Ubuntu/Debian you can use:
PHP5: sudo apt-get install php5-mysql
PHP7: sudo apt-get install php7.0-mysql
Lastly, to get it wo...