SQL - Chapter 1

SQL (Structured Query Language)

The gold standard for communicating with Relational Database Management Systems

Dr. Edgar F. Codd

IBM researchers developed the concept of relational databases based on who?

Structured English Query Language

What does SEQUEL mean?

SEQUEL

IBM created a language for their experimental relational database system, System R.

American National Standard Institute, 1986

This group adopted SQL as a standard in year?

1987

SQL became the International Organization Standard in what year?

Execute queries and retrieve data
Insert, update, and delete records
Create new database

What can SQL do?:

PostgreSQL
MySQL
Microsoft SQL Server

Different variations of SQL:

SELECT
UPDATE
DELETE
INSERT
WHERE

To be compliant with ANSI/ISO standard, languages should have these major commands:

Relational Database Management System

Datas are stored in tables

Table name
Record
Columns
Primary Key
Foreign Key
Data types
Constraints

Parts of an SQL table

Table name

The unique name that identifies the table in a database

Record

Represents a single, complete set of related data within the table. Also referred to as a row

Columns

A vertical structure in a table that represents a specific attribute or field of the data

Primary Key

A column that uniquely identifies each row in a table

Foreign Key

A column that establishes a relationship with a primary key in another table

Data Types

Specifies the type of data that can be stored in each column

Constraints

Rules applied to columns to maintain data integrity

NOT NULL
UNIQUE
DEFAULT
CHECK

Common constraints:

NOT NULL

Column must have a value

UNIQUE

All values in the column must be unique

DEFAULT

Specifies a default value for the column

CHECK

Ensures values meet a specified condition