When the queried data does not come from one table, you need to use multi table join to complete the query. Query the associated data according to the relationship between the data in different tables.
1, Cartesian product
In mathematics, the Cartesian product of two sets X and y, also known as the direct product, repr ...
Posted by grafnic1732 on Sun, 08 May 2022 20:34:12 +0300
var_dump("Contact PHP");//Code debugging uses this
php is a weak reference language, so it's easy to use.
1. Index array subscripts are numbers called index arrays 2. The subscript of associative array is a st ...
Posted by phenley on Sun, 08 May 2022 09:05:26 +0300
029 SQL basic query and data update
– workbench: Software
– query data: select //Query the name of fruit with a price of 10.2 yuan from the fruits table
select f_name(,f_price Better look) from fruits where f_price=10.2;
– query with in keyword: discrete value //Query s from the fruits table_ Records with IDS 101 an ...
Posted by spamyboy on Sat, 07 May 2022 23:01:58 +0300
Dock installs Redis (if installed, please skip this step)
1. Pull Redis image (latest version by default)
docker pull redis
If the download is slow, it is recommended to configure alicloud image
View alicloud image: alicloud official website -- > products -- > search container image service -- > management console
Mirror accelerator ...
Posted by asuperstar103 on Fri, 06 May 2022 23:50:35 +0300
Overview of MHA cluster
Introduction to MHA
MHA(Master high Availability)
It is developed by DeNA company in Japan. It is an excellent solution to realize high availability of MySQL. The automatic failover operation of the database can be completed within 0 ~ 30 seconds. MHA can ensure the consistency of data to the ...
Posted by eva21 on Thu, 05 May 2022 22:26:27 +0300
How to learn redis?
Learn what redis isHow to use redis, how to operate the data structure in redisTypical applications and operationsRead the redis source code
Redis is the abbreviation of Remote Dictionary Service; it is also a remote dictionary service; Redis is an in-memory database, KV database, data structure database; Red ...
Posted by cryp7 on Thu, 05 May 2022 16:53:18 +0300
1 check whether mysql service is installed by default in the system. If so, uninstall it. 1) Check command
rpm -qa|grep mysql
2) Uninstall command
rpm -e --nodeps mysql-libs-5.1.73-7.el6.x86_64
2 if it is CentOS 7, a mysql branch database mariadb will be installed by default. You must uninstall this database first 1) Search
rpm -e --node ...
Posted by newbie5050 on Thu, 05 May 2022 10:21:04 +0300
1. What is JDBC
JDBC (Java database connectivity) is a Java API for executing SQL statements. It can provide unified access to a variety of relational databases. It is composed of a group of classes and interfaces written in Java language. JDBC provides a benchmark by which more advanced tools and interfaces can be built to enable databa ...
GTID realizes master-slave replication data synchronization
GTID is a successfully executed global transaction ID generated based on the original mysql server. It consists of server ID and transaction ID. this global transaction ID is unique not only on the original server, but also on all mysql servers with master-slave relationship. Officiall ...
Posted by dharprog on Thu, 05 May 2022 06:29:39 +0300
For the deployment test conducted on the Ubuntu 18 version of the native simulator, refer to the official document:
hadoop: Link address
hive: Link address
The whole process is configured with the root account.
hadoop installation configuration
hadoop uses a virtual cluster, that is, a singl ...
Posted by anshu.sah on Thu, 05 May 2022 05:22:18 +0300