/SQL-practice-commands

SQL Practice Commands. Copied from command prompt after execution.

SQL COMMANDS (with important theory)

Query information_schema with SELECT

Information_schema is a meta-database that holds information about your current database. information_schema has multiple tables you can query with the known SELECT * FROM syntax:

tables: information about all tables in your current database
columns: information about all columns in all of the tables in your current database

SQL COMMANDS FROM COMMAND PROMPT

  • cd command to change the directory

    cd../..

    cd xampp/mysql/bin

    mysql -u root -p -h localhost

HOW TO SHOW DATABASES

show databases;

HOW TO CREATE DATABASE WITH PARTICULAR NAME

create database youtubestu;

HOW TO DELETE ANY DATABASES

DROP database youtubestu;

HOW TO CHANGE DATABASES

use youtubestu;

HOW TO SELECT DATABASES

select database();

HOW TO CREATE TABLE STUDENTS(TABLE NAME)

create table students
-> (
-> name varchar(55),
-> age int
-> );

HOW TO DESCRIBE A TABLE

desc students

HOW TO SHOW COLUMNS OF TABLE

show columns from studentsdemo;

HOW TO DELETE A TABLE FROM DATABASE

drop table studentsdemo;

HOW TO SHOW TABLES

show tables;

HOW TO INSERT INTO A TABLE

insert into studentdiff
-> (id, name, class)
-> values(1, 'vinod' , 5);

HOW TO SHOW THE TABLE**

select * from studentdiff;

WHAT IS NOT NULL DATA IN TABLE

NULLmeans that the value is not known of a field

create table stunull
-> (
-> id int not null,
-> name varchar(55) not null
-> );

HOW TO SET DEFAULT VALUES IN THE TABLE

create table studef
-> (
-> id int not null default 0,
-> name varchar(55) not null default 'unnamed'
-> );

HOW TO NEW FIELD IN TEH TABLE

insert into studef() values (); Query OK, 1 row affected (0.045 sec)

HOW TO NEW FIELD IN THE TABLE BY USING ALTER TABLE

alter table studef ADD class int;

WHAT IS PRIMARY KEY IN THE TABLE

CREATE TABLE stud_unique
-> (
-> stud_id INT NOT NULL,
-> name VARCHAR(55),
-> age INT,
-> PRIMARY KEY (stud_id)
-> );

HOW TO AUTO INCREMENT IN THE TABLE

CREATE TABLE stud_auto_
-> (
-> stud_id INT NOT NULL AUTO_INCREMENT,
-> name VARC(100),
-> age INT,
-> PRIMARY KEY (stud_id)
-> );