Tag:Main table

  • Performance considerations when mybatis handles one to many relationships


    Mybatis has three solutions for handling one to many situations: Join the sub table when querying, and then hand it over to mybatis to assemble When querying, do not join the sub table. In addition, initiate a select to retrieve the data of the sub table Similar to the second, but usingfetchType=lazyTo delay the capture […]

  • General operation of sub table


    Common methods of sub table front end //Clear child table rows // that.D002033Ffbcf094aa84f4affa531681d4516a100.ClearRows(); //Add child table row // var controlManager = this. D002033Ffbcf094aa84f4affa531681d4516a100;// Get sub table control object // var subObjectId = $. IGuid(); // Create row ID // controlManager.AddRow( subObjectId, { //”D002033ffbcf094aa84f4affa531681d4516a100. F0000001″: “hello”, // add data to sub table rows // }) //Update […]

  • MySQL connection query


    11.5 connection query (column connection) Question: there are ten pieces of data in the student table and ten pieces of data in the grade table. How many pieces of data are there after connection (Cartesian product): 10 * 10 = 100   Continuous query will produce Cartesian product; Suppose set a = {a, B}, set […]

  • Primary key, index design and paging query of hundreds of millions of rows of data in a single table


    1、 Overview Generally speaking, when designing the table structure of relational database system, we will classify the data according to the types of data. Generally, there are the following types: 1) Master data, whose data volume is basically stable and does not increase linearly with time. For example, branches, products and distributors. For this kind […]

  • (16) Building Dubbo distributed platform Dubbo service interface definition


    In the previous chapter, we started to introduce the relevant knowledge of Dubbo. On this basis, we can consider applying Dubbo services to our distributed system. Starting today, we will introduce in detail how to integrate Dubbo and spring and apply them to our distributed system. Create an ant bookmark facade project (Dubbo service interface), […]

  • 55. [database technology] [MySQL] multi table foundation


    1. Multi table overview Multiple tables are multiple tables, which are multiple tables in a database. In a database, there can be associations between tables. To better understand this part of multi table, it is best to understand some basic theories of database (the basic theory of relational database). 2. Foreign key constraint Foreign key […]

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


    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


    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


    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


    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


    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)


    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: […]