在MySQL提交事务之前,它将首先编写重做日志,然后提交事务,即预先写入日志。
start transaction;
update users set uuid = UUID() from user where id = 1
update users set uuid = UUID() from user where id = 2
update users set uuid = UUID() from user where id = 3
...
...
update users set uuid = UUID() from user where id = 1,000,000
// not y
MySql引发运行此sql的ProgrammingError
SELECT parents.uuid AS parents_uuid, children.uuid AS children_uuid,
children.parent_uuid AS children_parent_uuid,
count(*) OVER (PARTITION BY parents.uuid) AS children_count
FROM parents, children
WHERE children.parent_uuid = parents.uuid ORDER BY children_count DESC
我们希望测试mysql数据库中用于主键/索引的序列/bigint vs UUID(VERSION-4) VS UUID(version-7)的性能。对于mysql来说是个新手,很难找到一种简单的方法来轻松地创建数据卷,测试性能,并且“解释分析”在这里似乎也不起作用。基本上想做一些类似于下面的代码在postgres.Can中所做的事情,请在这里指导我?
(UUID Version-4是默认的随机UUID版本,Version-7是时间戳排序的UUID,它比随机的UUID更有顺序,因此在缓存方面更好)。希望以某种方式在mysql中生成这些数据并进行测试。
下面的代码在postgres中工作得很好,我
我正在尝试将一个包含1000万行UUID的CSV文件导入MySQL工作台中,这些UUID是用生成的。
首先,我创建了一个带有名为MySQL的binary(16)列的ID表。
CREATE TABLE TT (
ID BINARY(16) PRIMARY KEY);
接下来,我使用uuid库和UUID的二进制版本在Python中创建了一个1000万行CSV文件:
import pandas as pd
import uuid
ID = []
for i in range(10000000):
ID.append(uuid.uuid4().bytes)
Dict = {'ID
背景信息
系统
操作系统:
bash$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 6.0.5 (squeeze)
Release: 6.0.5
Codename: squeeze
MySQL:
bash$ mysql --version
mysql Ver 14.14 Distrib 5.1.63, for debian-linux-gnu (x86_64) using readline 6.1
数据库
引擎
知道为什么下面的VISIBLE会引起问题吗?
CREATE TABLE IF NOT EXISTS `setting` (
`uuid` INT(10) NOT NULL,
`type` VARCHAR(255) NOT NULL,
`code` VARCHAR(255) NOT NULL COMMENT 'An unique name.',
`value` MEDIUMTEXT NULL DEFAULT NULL,
`comment` LONGTEXT NULL DEFAULT NULL,
`created_on` INT UNSIGNED NOT N
mysql> USE bitcoin;
Database changed
mysql> CREATE TABLE btc ( uuid VARCHAR(36) NOT NULL, ign VARCHAR(20) NOT NULL, btc DOUBLE(30) NOT NULL, ) ENGINE=InnoDB;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right s
我有一个用php编写的简单的登录脚本,当我运行它时,它应该比较来自彼此的2个密码散列。这是im使用的代码;
$UUID = $_POST['UUID'];
$pass = $_POST['pass'];
// finds the same user where the uuid is the same as the one given in the post request
$query = "SELECT * FROM users WHERE UUID = '$UUID'";
$result = mysql_query($q
SQL查询:
SELECT
T.*,
U.nick AS author_nick,
P.id AS post_id,
P.name AS post_name,
P.author AS post_author_id,
P.date AS post_date,
U2.nick AS post_author
FROM
zero_topics T
LEFT JOIN
zero_posts P
ON
T.id = P.topic_id
LEFT JOIN
zero_players U
ON
T.a