Create database
CREATE DATABASE database_name;
The CREATE DATABASE command in MySQL is used to create a new database.
- CREATE DATABASE: Command that creates a new database.
- database_name: Name of the database you want to create. The name must be unique within the MySQL instance.
Notes:
- The database name must follow naming conventions and cannot contain certain special characters.
- If you try to create a database that already exists, MySQL will return an error. To avoid this, you can use the IF NOT EXISTS clause:
CREATE DATABASE IF NOT EXISTS database_name;
This version only creates the database if it does not already exist, avoiding errors.
View Database
SHOW DATABASES;
The SHOW DATABASES; command in MySQL is used to list all the databases available on the MySQL server instance you are connected to.
Example output:
+--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | | library_games | +--------------------+
Explanation:
- information_schema, mysql, performance_schema, and sys are system databases that MySQL uses to manage the instance itself and store information about privileges, performance, etc.
- Any other databases listed are those that were created by you or by other applications, such as the library_games database in this example.
This command is useful for checking which databases are available to manage or query.
Connect to database
USE database_name;
The USE database_name; command in MySQL is used to select a specific database and set it as the active database for the current session.
Create table
The CREATE TABLE command is used in MySQL to create a new table within a database. The basic syntax of the command defines the names of the fields (columns) and their respective data types.
CREATE TABLE table_name ( field1 data_type, field2 data_type, ... fieldN data_type );
Components:
- table_name: Name of the table you want to create.
- field1, field2, ... fieldN: Names of the columns (fields) that the table will have.
- data_type: The type of data that the column will store (such as INT, VARCHAR, DATE, etc.).
Practical example:
Suppose you are creating a table called games to store information about games, where each game has an ID, a title, a genre, and a release date:
CREATE TABLE games ( id INT AUTO_INCREMENT PRIMARY KEY, title VARCHAR(100), gender VARCHAR(50), release_date DATE );
Explanation:
- id INT AUTO_INCREMENT PRIMARY KEY: Creates an id column of type integer (INT), which increments automatically and is the primary key of the table.
- title VARCHAR(100): Creates a title column that can store texts of up to 100 characters.
- genre VARCHAR(50): Creates a genre column to store the genre of the game, with up to 50 characters.
- release_date DATE: Creates a column to store the release date of the game in date format (DATE).
Notes:
- It is important to define the correct data types for each field according to what you want to store.
- Defining a PRIMARY KEY ensures that the values ??in this column are unique for each row.
View contents of a table
The DESC command (or its full form DESCRIBE) is used in MySQL to display the structure of a table. It shows the column names, their data types, and other relevant information, such as whether the column allows null values ??or is part of a primary key.
CREATE DATABASE database_name;
ou
CREATE DATABASE IF NOT EXISTS database_name;
Example:
Suppose you want to see the structure of the games table created earlier:
SHOW DATABASES;
Example output:
+--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | | library_games | +--------------------+
Output Explanation:
- Field: Column name.
- Type: The type of data stored in the column (such as int, varchar, date).
- Null: Indicates whether the column allows null values ??(YES) or not (NO).
- Key: Shows whether the column is a key (PRI for primary key, UNI for unique key, MUL for index with duplicate values ??allowed).
- Default: The default value of the column, if any.
- Extra: Additional information, such as auto_increment.
This command is useful for quickly checking the structure of a table without having to look at the original creation code.
The above is the detailed content of MySQL Terminal: Create Databases, Tables and more.. For more information, please follow other related articles on the PHP Chinese website!
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