• Leetcode MySQL exercise one – employees who exceed the manager’s income


    The employee table contains all employees, and their managers also belong to employees. Each employee has an ID and a list of the ID of the manager corresponding to the employee. Id Name Salary ManagerId 1 Joe 70000 3 2 Henry 80000 4 3 Sam 60000 NULL 4 Max 90000 NULL The Department table contains […]

  • Summer self-study day 13 | database (VI) – multi table query


    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 […]

  • Summary of MySQL Basics


    Basic syntax of MySQL: MySQL data is available at the end of the article Execution sequence: from -> join -> on -> where -> groupby -> avg max .. -> having -> select ->order by SQL language classification: DQL: Data Query Language DML: Data Manipulation Language DDL: Data Definition Language DCL: data control language DQL […]

  • Employee test database statement


    1. Find all contents of the entire employee table.select *from employees2. View the employee name (last_name).select last_namefrom employees3. View employee number, name, and type of work.select last_name,job_id,employee_idfrom employees4. Displays the names and wages of all employees and displays department_ The ID is displayed as (department_id).select last_name,salary,DEPARTMENT_ID as Department_Idfrom employees5. Find employees working in department 60.select […]

  • Learning notes: MySQL query


    Preface: I spent two nights watching mysql. I didn’t expect that the effect was too poor. It’s better to follow the online class video and complete the exercise questions (if you don’t write notes on the exercise questions, you won’t record them), and then take notes. 1、 Basic query select statementSyntax: select query list from […]

  • MySQL exercise


    1.Name of the person with the highest salary in each department Solution: 1. Ask for the highest salary of each department first SELECT e.deptno,MAX(e.sal) as maxsal from emp e GROUP BY e.deptno; 2. Take the results obtained in the first step as a temporary table SELECT e.deptno,ename,t.maxsal,e.sal from (SELECT e.deptno,max(e.sal) as maxsal from emp e […]

  • Analytic function


    concept Official definition: Analytic functions compute an aggregate value based on a group of rows. They differ from aggregate functions in that they return multiple rows for each group. The group of rows is called a window and is defined by the analytic_clause. For each row, a sliding window of rows is defined. The window […]

  • Front end training – intermediate stage (43) – Vue 2. X actual combat curd


    The most basic of the front end isHTML+CSS+Javascript. If you master these three technologies, you can get started, but you are only getting started. Now the definition of front-end development is far more than that. Front end classroom(HTML/CSS/JS)In order to improve the level of technology and lay a solid foundation of knowledge, we have a […]

  • Mybatis select record encapsulation


    Select record encapsulation Returns a list collection. Resulttype writes the type of the elements in the collection <!– public List<Employee> getEmpsByLastNameLike(String lastName); –> <!– Resulttype: if a collection is returned, write the type of the elements in the collection — > <select id=”getEmpsByLastNameLike” resultType=”com.atguigu.mybatis.bean.Employee”> select * from tbl_employee where last_name like #{lastName} </select> Returns the […]

  • IView form user defined verification, prompt information does not disappear


    IView form user-defined verification. After opening the bullet box, the red prompt message of the parent bullet box does not disappear,Because the parent bullet box does not receive the information of the bullet box; resolvent //Write the position above the data return const validate_dept = (rule, value, callback) => { value = this.addInfo.deptId || this.modifyInfo.deptId […]

  • C # MVC layui realizes two-level linkage of drop-down box


    1 layui.use 1. Official use document of layui: HTTPS :// www . layui . com / doc / 2. The built-in module of layui is not loaded by default. The module will not be loaded until the method of starting the module is executed; 3、 layui.use It’s a way to load modules.The code is as […]

  • Basic summary of orcla (2)


    Set operator Notes on using set operator Column names and expressions in the select list should correspond to * * quantity and data type * * Parentheses can change the order of execution Order by clause: Can only appear at the end of a statement You can use the column name, alias, or relative position […]