Tag:Main table

  • Summer self-study day 11 | database (IV) – constraints

    Time:2021-10-24

    Series articles: Summer self-study day 09 | database (I) – SQL, DDL Summer self-study day 10 | database (II) – DML Summer self-study day 10 | database (III) – DQL Summer self-study day 11 | database (IV) – constraints Summer self-study day 12 | database (V) – multi table, database design Summer self-study day 13 […]

  • MySql-Day-02

    Time:2021-10-19

    MySQL query DQL & multi table relation Ability to query data using SQL statements Ability to use SQL statements for conditional queries Ability to sort using SQL statements Ability to use aggregate functions Ability to use SQL statements for grouping queries Be able to complete data backup and recovery Be able to use visualization tools […]

  • MySQL Basics

    Time:2021-10-7

    MySQL table query statement DQL: query statement Sort query Syntax: order by clause Sort by: ASC: ascending, default Desc: descending order. be careful: If there are multiple sorting conditions, the second condition will be judged only when the condition values of the current edge are the same SELECT * from userinfo ORDER BY age ASC,id […]

  • MySQL learning notes (5) — constraints

    Time:2021-6-23

    Concept: limit the data in the table to ensure the correctness, validity and integrity of the data. Classification: 1. Primary key constraint: primary key 2. Non NULL constraint: not null 3. Unique constraint 4. Foreign key constraint: foreign key Non NULL constraint: not null, value cannot be null 1. Add constraints when creating tables CREATE […]

  • PHP combined with MySQL 10 million level data processing

    Time:2021-6-9

    Thinking of MySQL table A 100 million order table can be divided into five tables, so that each table has only 20 million data, sharing the pressure of the original table. Sub tables need to be divided according to certain conditions. Here, tables can be divided according to regions. A middleware is needed to control […]

  • Oracle initial (day 1)

    Time:2021-5-3

    1、 Database classification 1. Small database: access, FOXBASE 2. Medium sized databases: Informix, SQL server, MySQL 3. Large databases: Sybase, DB2, Oracle 2notes   1./* November 6, 2020 This is a multiline comment in Oracle   */ 2. — this is a single line comment for Oracle   3、 Common commands 1. Data type (1) Character type: […]

  • PHP + MySQL 10 million level data processing case (1) (sub table)

    Time:2021-4-26

    A series of articles: PHP + MySQL 10 million level data processing case (2) significance of sub table PHP + MySQL 10 million level data processing case (1) (sub table) Cut the crap and go straight to the sceneA financial company has 500 W investment users, and 50 W investments are recharged every day. So […]

  • A slow query optimization of MySQL

    Time:2021-2-4

    Recently, I met a slow query problem in mysql, so I checked it. Here is a summary of the related process. Positioning reasons First of all, I checked the slow query log of MySQL and found that such a query takes a long time (about more than one second) and scans a large number of […]

  • Basic knowledge of MySQL

    Time:2021-1-17

    MySQL table query statement DQL: query statement Sort query Syntax: order by clause Sort by: ASC: ascending order, default Desc: descending order. be careful: If there are multiple sorting conditions, the second condition will be judged only when the condition values of the current edge are the same SELECT * from userinfo ORDER BY age […]

  • MySQL constraints

    Time:2021-1-16

    Concept: limit the data in the table to ensure the correctness, validity and integrity of the data. Classification: Primary key constraint: primary key Non NULL constraint: not null Unique constraint: unique Foreign key constraint: foreign key Non NULL constraint: not null, value cannot be null Add constraints when creating tables CREATE TABLE stu( id INT,Name […]

  • Net / NETCORE /. Net5 ORM six query systems – sqlsugar advanced

    Time:2021-1-10

    Framework introduction Sqlsugar ORM is an old domestic ORM framework with strong vitality. From the early immature stage of ORM, it has survived until now. Why should I insist on it all the time? That’s because there are still many users using it. I could have launched the new open source framework earlier However, users […]

  • Learning SQL Server (2): data table constraints

    Time:2020-12-23

    –Data table constraint: by making some rules, the data stored in the database is standardized, correct and complete. –Non NULL constraint the field cannot be empty keyword: not null –The value of the unique constraint field cannot be repeated in this table and can be null, but only once. Keyword unique –The default constraint gives […]