check constraint means to filter one or more columns according to certain preset rules. If the condition is true, the filtering succeeds; if the condition is false, the filtering fails and the failure code is returned to the client.
Why do you want to list and write this separately? You often encounter irregular SQL. In many cases, you can onl ...
Added by AndyB on Wed, 13 May 2020 12:25:22 +0300
Original address: https://mysqlserverteam.com/mysql-8-0-innodb-now-supports-instant-add-column/
For a long time, instant DDL has been one of the most popular InnoDB functions. For the growing and fast-growing data set, any network scale database must have the function of executing DDL immediately.
Developers often need to add new columns to m ...
Added by coolfool on Tue, 12 May 2020 16:55:02 +0300
Redis is an open source, network-enabled, memory-based and persistent log, Key-Value database written in the ANSI C language, and provides multilingual API s.
This article focuses on the main scenarios for using Redis with PHP.
Simple String Cache Actual
$strCacheKey = 'Test_bihu';
//SET Application ...
Added by chadbobb on Tue, 12 May 2020 09:51:38 +0300
Currently used user and host:
mysql> select USER();
| USER() |
| root@localhost |
1 row in set (0.00 sec)
Before mysql 5, you can directly use INSERT to INSERT mysql users into mysql tables. You can't do this after mysql 5
mysql> insert into mysql.user(Ho ...
Added by snap2000 on Mon, 11 May 2020 19:06:52 +0300
1, Create your own database
Download and install MySQL
1.windows Download: http://dev.mysql.com/downloads/mysql/
2. Open the server: enter the bin directory of the download path in the terminal (cmd), and execute mysqld -- initialize executor to start the server and initialize, but an error will be reported. The reason is that there is no data ...
Added by _giles_ on Mon, 11 May 2020 07:51:35 +0300
7, MySQL client tools and SQL introduction
mysql client command introduction;
How to get help from mysql;
Management database of DDL statements;
DDL statement management table and case introduction;
Data in management table of DML statement;
SELECT to retrieve data;
2. mysql interface program and SQL introduction
mysql client comma ...
Added by jdimino on Fri, 08 May 2020 16:47:04 +0300
Background: for a recent countdown learning time recording project, you need to record the progress of the current page when the user clicks the back button of the browser or directly closes the browser, or directly exits wechat or enters the background. The next time you go in, you need to start the countdown from the last place you left. At f ...
Added by edgev on Fri, 08 May 2020 13:39:14 +0300
[contents] (the rest are knowledge)
Three Affairs (mastery)
Four stored procedures
Vi. process control
7, Index theory
1. What is a view
A view is a virtual table (non real existence). Its essence is to get a dynamic data set according to SQL statements and name it. When users use it, they only ne ...
Added by csplrj on Fri, 08 May 2020 11:46:25 +0300
The charge system in the computer room is half developed. From blind helplessness at the beginning to being able to proceed slowly now, it is a small progress. The basic data setting window in the computer room charging system is a very important window in the whole software. When I open the database software, I see that there are many pieces o ...
Added by aquilla on Wed, 06 May 2020 03:28:31 +0300
Spring's JDBC module is responsible for database resource management and error handling, which greatly simplifies the operation of the database by the developers, so that the developers can get rid of the tedious database operation, so as to put more energy into writing business logic.
For the Spring framework of database operation, the JdbcTem ...
Added by twilitegxa on Tue, 05 May 2020 09:44:21 +0300