Programmer Think

One: Preparing data #Create tables and insert records CREATE TABLE class ( cid int(11) NOT NULL AUTO_INCREMENT, caption varchar(32) NOT NULL, PRIMARY KEY (cid) ) ENGINE=InnoDB CHARSET=utf8; INSERT INTO class VALUES (1, 'Class Two, Three Years'), (2, 'Three-year shift'), (3, 'Class Two a Year'), (4, 'Nine Classes in Two Years'); CREA ...

Summer vacation summary During the summer vacation, I mainly write a small program project and modify another small program. The following mainly introduces the project experience and technology Start of SC project Step 1: get the project and write the development documents first, mainly to design the database (designing the database is the ...

Indexes Unique index: a unique index does not allow two rows to have the same index valuePrimary key index: defining a primary key for a table will automatically create a primary key index, which is a special type of unique index. The primary key index requires that each value in the primary key is unique and cannot be emptyClustered index ...

catalogue Start sql journey Exercise 1: count the number of tables in the dataset Exercise 2: explore the summary of the table Exercise 3: create a crime map Select/From/Where simple query Exercise 1: identify countries that use ppm Exercise 2:   select * query all fields Group by&Having&Count  Exercise 1: find out the a ...

Base Query 1. Grammar The select query list from table name is similar to System.out.println (print stuff) 2. Characteristics 1. Query lists can be: fields in tables, constant values, expressions, functions 2. Query results can be a virtual table 3. Examples 1. Query a single field: select field name from table name; 2. Query multipl ...

Explain The difficulty of the basic exercises is fairly simple, but there are still some details to master. The main purpose of this topic is to familiarize yourself with the basic queries of SQL statements, so you can understand the statements about table building, because in general development, tables are built graphically, while SQL sta ...

Important notes about MyBatis2 are in the following Baidu network disk connection. Welcome to learn together Link: https://pan.baidu.com/s/1zGAtbdQElMTgzUZUSg033w Extraction code: 2ywn Here are some easily forgotten points in my learning process to make another record for follow-up review Step 1: write mybatis configuration file <?xml ver ...

The leaf segment mode is an optimization to directly use the self increment ID of the database as the distributed ID to reduce the frequency of database operation. It is equivalent to obtaining self incrementing IDs from the database in batches. One number segment range is taken out from the database each time. For example, (11000] represents 1 ...

1.redis client tool jedis 1.1 Introduction and preparation of jedis Introduction to 1.1.1 jedis Jedis is a client in Java that operates on redis, similar to accessing the mysql database through jdbc. To implement jedis in java's mevan, you need to import the following dependencies: <dependency> <groupId>redis.clients</g ...

Catalog 1. Understanding MHA 1. Overview of MHA 2. Composition of MHA 3. Characteristics of MHA 4.MHA cluster architecture diagram  2. Build MySQL MHA 1. Construction of MHA 2. Fault simulation  Algorithms for failover alternate primary libraries: Failure Repair Steps: 1. Understanding MHA 1. Overview of MHA MHA (Mast ...