1. MySQL database basics, 1. mysql database

1. MySQL database basics, 1. mysql database
1. MySQL database Basics

Display the current server version select version ();

Display the current date and time select now ();

Displays the select user () of the current USER ();

View database show databases;

View the warning show warnings;

2. MySQL statement specifications

(1) All keywords and function names are in uppercase;

(2) The database name, table name, and field name are all in lowercase;

(3) The SQL statement must end with a semicolon.

3. Create a database

CREATE {DATABASE | SCHEMA} [if not exist] db_name [DEFAULT] character set [=] charset_name; here "{}" indicates a required parameter, "|" indicates the selection from these items, "[]" indicates the option, and generally indicates the judgment item. Create database | SCHEMA db_name is required, and other items may exist. The character set clause is used to specify the default database character set. For example:

Create database user1;

4. Modify the database

ALTER {DATABASE | SCHEMA} [db_name] [default] character set [=] charset_name;

5. delete a database

DROP {DATABASE | SCHEMA} [if exists] db_name;

Summary:

MySQL Default port: 3306

MySQL Super User: root

CREATE DATABASE

Modify DATABASE: ALTER DATABASE

Delete database: DELETE DATABASE

6. Data Type

Data type refers to the data features of columns, stored procedure parameters, expressions, and local variables. It determines the data storage format and represents different information types. One of the principles of Data Optimization: select the best and most appropriate data type, rather than the largest data type.

(1) INTEGER (age, etc)

　　

(2) floating point

　　

(3) Date and Time

　　

(4) balanced