DDL

#DDL--DATA DEFINITION LANGUAGE
#----------Library-----------------
#Create a database
CREATE DATABASE day19;
#Create a database encoded as utf8
CREATE DATABASE day191 CHARSET UTF8;

#Display all database names
SHOW DATABASES;

#View database creation information
SHOW CREATE DATABASE day191;
SHOW CREATE DATABASE day19;
SHOW CREATE DATABASE ex01;

#Delete the specified database
DROP DATABASE day191;

#View the database in use
SELECT DATABASE();

#Choose to use a database
USE day19;
#View the database in use
SELECT DATABASE();

#Display all tables in the library
SHOW TABLES;

#----------surface--------------
#Create table and add fields
CREATE TABLE abc(
aid INT PRIMARY KEY,
aname VARCHAR(20) NOT NULL UNIQUE,
age INT NULL);

CREATE TABLE abcd(
did INT PRIMARY KEY,
dname VARCHAR(20),
ddate DATE
);

#Show table structure
DESC abc;
DESC abcd;

#Delete table abcd
DROP TABLE abcd;
#Show all tables
SHOW TABLES;

#Modify table-add column
ALTER TABLE abc
ADD hobby VARCHAR(24) NULL DEFAULT '0';
#Show table structure
DESC abc;

#Modify table-delete column
ALTER TABLE abc
DROP hobby;
#Show table structure
DESC abc;

#Modify the data type and constraints of the column
ALTER TABLE abc
MODIFY aage VARCHAR(20);
DESC abc;

#Modify field name
ALTER TABLE abc
CHANGE age age DOUBLE(3,2) NOT NULL DEFAULT 0;
DESC abc;

#Modify table name
RENAME TABLE abc TO bbc;
DESC bbc;

RENAME TABLE BBC TO ABC;
DESC abc;

The above is the detailed content of DDL. For more information, please follow other related articles on the PHP Chinese website!