个， 假如排序在最后一条语句后面加order by;（重复自动去除）union all:
select user_id from user union all select user_id from toy order by user_id;As with union, all values are returned in the result of the Union all, not the copy of each value, and the repetition of the package is also listed.
To create a table with union:create table m_union as select user_id from user union select user_id from toy;//这样会把user里的user_id和toy表里的user_id的内容都拿出来放到心创建的m_union表格里。INTERSECT,EXCEPT
Intersect is the intersec
MySQL queries, subqueries, join queries, federated queriesI. MySQL query five seed sentencewhere (conditional query), having (filter), GROUP by (grouping), order by (sort), limit (limits the number of results)Two. Sub-query1.where Sub-querySELECT * from Tb1 WHERE cat_id in (the Select Max (ID) from the TB2 GROUP by cat
Use of mysql monitor MONyog and mysql monitor monyog
MONyog is a commercial paid software, but you can find the cracked version. I use the 4.72 cracked version.
In the server settings, 1.1. Enable sniffing in Sniffer Settings? Select YES to enable Sniffer, and then setFilteringOptions,The Long Running Que
Monitoring over 250 configuration parameters and thousands of measurements is not an easy task for Oracle administrators to monitor the overall health of their Oracle databases. Oracle provides a variety of tools to monitor performance, but this is still too much. To effectively monitor the health of your Oracle database, you need to familiarize yourself with the
Shell scripts monitor MySQL services and shell scripts monitor mysqlThe main content of this article describes how to monitor whether the MySQL service is normal by using shell scripts. For more information, see
The general idea is to check whether the
The Zabbix version currently in use is 2.2.3, which comes with MySQL monitor template templates App MySQL, with only a few monitoring items. If you just want to do basic monitoring of MySQL, you can use this template, if you want to monitor the various
Mybatis queries the time period of mysql, and mybatis queries mysql
The mapper file is written as follows: (fuzzy query, query time range)
Mysql time period Query
Your request is between '2017-7-12 11:18:54 'and '2017-7-12 11:22:20 '.Apparently, 11:18:46
Mysql buffer queries and non-buffer queries, mysql Buffer
Recently I encountered the following error when developing a PHP program:
PHP Fatal error: Allowed memory size of 268 435 456 bytes exhausted
The error message shows that the maximum allowed memory is exhausted. I was surprised at first when I encountered such a
MySQL Buffered and unbuffered queries
Today we are going to talk about the advanced function of MySQL query cache, that is, query cache and query non-cache!
Cause: (Memory overflow warning)
PHP Fatal error:allowed Memory size of 268 435 456 bytes Exhausted
The main saying is that the cache query is all at once to find out the contents, put in memory,
Download and install Percona source, use Percona Toolkit or Innobackup later
Wget-n--no-check-certificate RPM-IVH percona-release-0.1-4.noarch.rpm2. Installing the Percona Monitor plugin with YumYum-y Install Percona-zabbix-templatesAfter the installation, most of the files are placed under the/var/lib/zabbix/percona directory3. Create a new/conf.d/directory under the Zabbix_agent folder and copy the installation generated Percona monitoring prof
Tags: poi oca verify sudo link manually load TAC add1. Monitor MySQL with the Percona monitor pluginYum Install http://www.percona.com/downloads/percona-release/redhat/0.1-3/percona-release-0.1-3.noarch.rpmHttps://www.percona.com/doc/percona-monitoring-plugins/1.1/zabbix/index.html#installation-instructionsYum Install percona-zabbix-templates PHP php-mysql1.php s
Multi-to-many queries, three-table queries, mysql statement This post was last edited by setoy from 2015-02-0615: 11: 52 Common Application: Data tables of articles and labels, then query a tag, such as "technology", to query all technical articles. Article table article: nbsp; aid, nbsp; title, content ------------ multi-to-many
Optimizing Nested Queries
nested queries (subqueries) You can use the SELECT statement to create a single-column query result, and then use the result as a filter in another query. Nested queries are simple to write and easy to understand. However, it can sometimes be replaced by a more efficient connection (join).
Now, if you want to find out customers who have
[Mysql] basic concepts of primary keys and Foreign keys for multi-table queries using inner join and nested queries
Although multi-table queries are required in computer science and databases, many teachers have not thoroughly explained this difficulty. It's confusing to have a bunch of things that are connected to the
file under/usr/local/zabbix/etc/zabbix_agentd.conf.d/directoryFinally restart the ZABBIX_AGENTD, the Template App MySQL to join the monitoring is OK, also good:650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M00/4A/F2/wKiom1QnfByBA6WBAATJ3XaOf1c330.jpg "style=" float: none; "title=" 1.png "alt=" Wkiom1qnfbyba6wbaatj3xaof1c330.jpg "/>650) this.width=650; "src=" http://s3.51cto.com/wyfs02/M02/4A/F4/wKioL1QnfEWwL1etAAVJQTIh1nI224.jpg "style="
Multi-to-many queries, three-table queries, evaluate mysql statements for common applications: articles and tag data tables, and then query a tag, such as "technology", to query all technical articles.
Article table article:
Aid, title, content ------------------------------------- 1 Qt assists in cross-platform application development, 2 Qt assists in cross-
table i_student, but the actual student table i_student often not only two columns of information. Through a simple sentence can not be simpler, all the database must know the statement to find out the entire student table i_student Name column name:Select Id,name from I_studentThe query results are as follows:3, set the first step of the query results for T1, the second step of the query result is T2, the T1 and T2 two tables connected together, only the retention ID and student_id correspondi
Optimization of mysql nested queries and nested query of table queries is poorly optimized as I mentioned above. Without special considerations, table queries are more effective than nested queries. Although the two queries share
MySQL Transaction Handler
InnoDB Adaptive HashindexShows the use of Adaptive hash Index , which can only be used to search for an equivalent query .# Hash Table Size 17700827, node heap has 35112 buffer (s)# 3577.42 Hash searches/s, 507.49 non-hash searches/s
Hash Index Cells TotalThe number of slots in the adaptive hash table =innodb_buffer_pool_size/256
Hash Index Cells
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