Knowledge of JDBC
1. Concept: Java database connectivity, Java database connection, Java language operation database
JDBC essence: it is actually a set of rules defined by the official (sun company) to operate all relational databases, that is, interfaces. Each database manufacturer implements this interface and provides database driver jar package. We can use ...
Added by Pehape on Mon, 21 Feb 2022 06:58:21 +0200
Mysql index principle and slow query optimization
background
MySQL has become the first choice for most companies with low-cost and rich Internet resources. Although the performance is excellent, how to better use the so-called "good horse with good saddle" has become a compulsory course for development engineers. We often see requirements such as "proficient in MySQL", &q ...
Added by marms on Mon, 21 Feb 2022 06:53:35 +0200
MySQL's slow query and slow log and the use of mysqldumpslow and Pt query digest slow query log analysis tools
Slow query and slow log
Query and start of slow log
Query whether the slow log is enabled
mysql> show variables like 'slow_query_log';
+----------------+-------+
| Variable_name | Value |
+----------------+-------+
| slow_query_log | OFF |
+----------------+-------+
1 row in set (0.00 sec)
Enable slow query log
# It is convenien ...
Added by jscix on Mon, 21 Feb 2022 03:46:26 +0200
The sub query of MySQL learning notes is the sub query after the keywords select, from, where and exists
1, Meaning of subquery
Meaning: select statements that appear in other statements are called subqueries or intra queries; The external query statement is called primary query or external query Classification:
According to the location of sub query: After select: only scalar subqueries are supported After from: only table subqueries are ...
Added by sullyman on Sun, 20 Feb 2022 19:44:44 +0200
How should I configure the server after spending 288 for three years
preface
The ECS that Alibaba cloud bought for 95 yuan is about to expire. It needs more than 1000 to renew. I thought there was nothing important on the server, so I took advantage of Tencent cloud discount and spent 288 to buy a three-year CVM. CVM is a cloud virtual machine. Let's call it a server for the time being.
1 core 2G, it seems tha ...
Added by dch27 on Sun, 20 Feb 2022 19:06:18 +0200
Day 12 of MySQL Introduction (database configuration and deployment)
catalogue
12.1MySQL configuration file
(1) Configuration section
(2) Basic configuration
(3) Memory and optimized configuration
(4) Log configuration
12.2 data backup and restore
(1) Data backup
(2) Data restore
(3) Binary log
12.3 multi instance deployment
12.4 master slave replication
12.1MySQL configuration file
(1) Configu ...
Added by sun14php on Sun, 20 Feb 2022 16:11:48 +0200
The connection query of MySQL learning notes (this article only introduces the connection query of SQL 92 standard in detail) uses where for connection query
Connection query (this article only introduces the connection query of SQL 92 standard in detail)
1, Meaning and classification of connection query
meaning:
Also known as multi table query, join query will be used when the query fields come from multiple tables Cartesian product phenomenon:
Suppose that table 1 has m rows, table 2 has n ...
Added by deljhp on Sun, 20 Feb 2022 10:54:30 +0200
SQL notes (compact version)
Database structure diagram
1. Retrieve data
1.1 select database
USE sql5th;
1.2 select a single column
select prod_name from Products;
+---------------------+
| prod_name |
+---------------------+
| Fish bean bag toy |
| Bird bean bag toy |
| Rabbit bean bag toy |
| 8 inch teddy bear |
| 12 inch teddy bear |
| ...
Added by sc00tz on Sun, 20 Feb 2022 09:13:52 +0200
Sharding JDBC sub database and sub table (I)
1 Overview
1.1 what are the sub warehouse and sub table
Xiao Ming is a developer of a start-up e-commerce platform. He is responsible for the function development of the seller module, The related businesses of shops and commodities are involved, and the design is as follows Database:
Store information and geographical area inform ...
Added by new_programmer on Sun, 20 Feb 2022 07:09:11 +0200
mysql database topic
– one Prepare data
Four tables are known as follows: Student form: student (student number, student name, date of birth, gender) Transcript: score (student number, course number, grade) Course schedule: Course (course number, course name, teacher number) Teacher form: teacher (teacher number, teacher name) Write the corresponding SQL sta ...
Added by corbin on Sun, 20 Feb 2022 03:58:46 +0200