$ sudo apt-get install mysql-server

$ sudo apt-get install sqlite3

$ sudo apt-get install postgresql

添加：
mysql> CREATE USER 'user1'@'localhost' IDENTIFIED BY 'pass1';

mysql> GRANT ALL PRIVILEGES ON *.* TO 'finley'@'localhost'WITH GRANT OPTION;
删除：

mysql> DROP USER 'user1'@'localhost';

$ sudo adduser user1 #先在系统中添加一个用户

$ sudo su - postgres

postgres@debian:~$ psql

postgres=# CREATE USER user1 WITH PASSWORD 'password';

删除用户：
postgres=# DROP user user1;

$ mysql -u jack -p
mysql> \q

$ sqlite3

sqlite> .q

$ psql -U user1 -d exampledb
exampledb=> \q

mysql> CREATE DATABASE abc;
mysql> DROP DATABASE abc;

$ sqlite3 abc.db

$ rm abc.db

postgres=# CREATE DATABASE exampledb OWNER user1;

postgres=# GRANT ALL PRIVILEGES ON DATABASE exampledb to user1;
只有给user1用户赋予创建数据库的权限后他才能创建数据库！这里user1用户只是对exampledb数据库有操作权限。

postgres=# CREATE DATABASE db1;
postgres=# DROP DATABASE db1;

mysql> CREATE TABLE tb1(id int auto_increment,name varchar(),primary key(id));

mysql> DROP TABLE tb1;

sqlite> CREATE TABLE users(id integer primary key autoincrement,name text,age int);

sqlite> DROP TABLE users;

exampledb=> CREATE TABLE users(id serial,name VARCHAR(), signup_date DATE);
exampledb=> DROP TABLE users;