Programmer Think

Advanced 1. Direct query – single field in query table – select sNo from student; – single field in query table – select sNo, sName from student; – query all fields in the table select * from student; Note: which library to use when querying all fields 2. Query constant value select 100; select 'male'; ...

preface Recently, a course experiment needs to be configured with the environment shown in the title, so the author takes this opportunity to use docker to build a returnable container experiment environment to complete the experiment, and also records some errors encountered in the construction process. 1, Environmental description ...

1, How many constraints do you master in MYSQL? In MYQSL, there are some constraints. For example, it cannot be null or must be unique. Like ID cards, everyone's ID number is unique. Gender can be male or female, but not null. The following describes six constraints in MYSQL 1. NOT NULL: a constraint column cannot be empty. -- Cre ...

Part 1: init initializes MySQL connection related API s: (1) mysql_init : MYSQL* mysql_init(MYSQL *mysql); Returns a MySQL handle. Corresponding to this handle, MySQL will allocate an object in the database and open up memory to store the processing information associated with the connection. All subsequent operations on this database conne ...

Book constructor The Book object is divided into two scenarios: Parse the Book object directly from the e-Book fileGenerate Book object from data object class Book { constructor(file, data) { if (file) { this.createBookFromFile(file) } else { this.createBookFromData(data) } } createBookFromFile(file) { cons ...

preface: Hello, guys, I'm running snail rz. Of course, you can call me snail Jun. I'm a rookie who has studied Java for more than half a year. At the same time, I also have a great dream, that is, to become an excellent Java Architect one day. This Mybatis basic learning series is used to record the whole process of learning the basic ...

DQL data query language 1, SQL overview 1. What is SQL * * SQL (Structured Query Language) * * is a "structured query language", which is an operation language for relational databases. It can be applied to all relational databases, such as MySQL, Oracle, SQL Server, etc. Although SQL can be used in all relational databases, many ...

Java cultivation program -- the 68th day of learning punch in Java (punch in the 68th day) MySQL multi table connection query (MySQL 99) Yesterday, we shared the multi table MySQL l92 syntax of MySQL. The disadvantage of this syntax is to mix the multi table connection conditions with the common filter conditions. At the same time, ...

The interviewer gave a dead order: three servers and build a MySQL master-slave architecture. Can you handle it? I saw that there were 20 minutes before the next interview. OK, I'll finish it for you in 10 minutes and write the document. 1, System experiment environment [root@itlaoxin162 ~]# uname -r 3.10.0-1062.12.1.el7.x86_64 The ker ...

1, Single table query Query: users get the data they need from the database table in different ways It is very important and frequent in database operation 1.1 create database 1. Create a new library company 2. Create EMP (employee table) in the company library emp(Employee number empno Employee name empname Employee's p ...