Structured Query Language — Part 1: Defining Tables and Writing Queries: visual lesson, CBSE Class 12 Computer Science

Lesson

Structured Query Language (SQL)

Part 1 — defining tables and asking questions of the data with SELECT.

In this lesson you will

Tell DDL from DML and choose suitable data types and constraints for a table
Use database and table commands: CREATE, USE, SHOW, DESCRIBE, ALTER and DROP
Write SELECT queries with WHERE, DISTINCT, aliases, IN, BETWEEN, LIKE, IS NULL and ORDER BY, and predict their results

Part 1 at a glance

Concept

SQL is the standard language of relational databases such as MySQL.

Table of the advantages of SQL: declarative, standard, English-like, powerful, and shared and safe with constraints
Feature of SQL	What it means for you
Declarative	You state what data you want; the database decides how to fetch it
Standard	The same core commands work in MySQL and other relational databases
English-like	`SELECT`, `FROM`, `WHERE` read almost like sentences
Powerful	One query can filter, sort, group and combine thousands of rows
Shared and safe	Many users can work on the same data with keys and constraints keeping it correct

Concept

Some commands shape the containers; others work on the contents.

Table comparing DDL, which works on structure with CREATE, ALTER and DROP, and DML, which works on rows with INSERT, UPDATE, DELETE and SELECT
Category	Works on	Commands
DDL (Data Definition Language)	Structure of databases and tables	`CREATE`, `ALTER`, `DROP`
DML (Data Manipulation Language)	Rows of data in tables	`INSERT`, `UPDATE`, `DELETE`, `SELECT`