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Introduction to SQL SQL(Structured Query Language) is a set of relational database management system (RDBMS) for management, which is based on ANSI (American National Standards) Institute (American National Organization for Standardization) standard computer language, the more important version is SQL92In addition to supporting standar ...

catalogue 0 problem description 1 problem solving 2 Summary 0 problem description SQL extracts string elements from a fixed location. You have a string that contains a continuous piece of log data. You want to parse the string and extract some information from it. However, the information you need does not exist in the fixed position of t ...

SQL Server group query and connection query Group query using GROUP BY Multi column grouping query Group filtering using HAVING clause Classification of multi table join queries External connection query 1, Group query using GROUP BY The above type of query is called group query in SQL Server. Group query is implemented by GROUP BY cl ...

2021SC@SDUSC Today's analysis is the search function File at Web page initialization Use a template library search_ sort ASC in model renders this web page Set the title of the web page as "full site search" Then check the configuration of full-text search first Search the mysql database for variables and assign values ...

I Single-Row Functions Note: dual is a virtual table and cannot save any data. There is only one field and one row of records 1. Semantics The single line function returns a result for each record 2. Character function 1.lower(): convert to lowercase, upper(): convert to uppercase, initcap initial capital select lower(ename) from emp; 2 ...

This note is the learning content of Alibaba cloud Tianchi Longzhu plan SQL training camp. The link is: https://tianchi.aliyun.com/specials/promotion/aicampsql； Summary of learning points: 1. Addition and subtraction of tables union, except 2. Connect the join Learning content: 1. Table addition union: SELECT product_id, product_nam ...

Learning notes on common database operations 1, How to create a new table Here is a table for creating user2: CREATE TABLE if NOT EXISTS user2( username VARCHAR(50) not NULL, password VARCHAR(50) NOT NULL, realname VARCHAR(50), phone VARCHAR(50), userid int AUTO_INCREMENT, PRIMARY key(userid) )ENGINE=InnoDB DEFAULT CHARSET=utf8; Ins ...

1. Single table query 4.1 basic query statement Query the contents of the field Name and Salary; Query the contents of the whole table. USE Company; #Please add the implementation code here ########## Begin ########## ########## retrieving the Name and Salary ########## select Name,Salary FROM tb_emp; ########## retrieving all the tab ...

Analysis of JDBC core technology Database connection pool 1. Necessity of JDBC database connection pool When developing web programs based on database, the traditional mode basically follows the following steps: Establish database connection in the main program (such as servlet and beans)Perform sql operationsDisconnect database Pro ...

1. Introduction to SQL SQL is a structured query language. It is a set of operation commands specially established for database. It is a database language. The interactive operation of the database is inseparable from SQL, which provides great convenience for us to manage the database. 1.1 database use case construction Note: all of ...