SQL

• stands for structured query language.
• allow user to query, transform and manipulate data.
• SQL used in mobile and websites.

Relational databases

• the model of relational database, it’s like an excel spreadsheet that contain tables.
• these tables are two-dimentional tables.
• each table contain fixed number of columns and N number of rows.
• for example, if I want list of most used cars model in Amman and information related to it, such as it’s mode, number of wheels, number of doors, year created.
• and we might want to know which car license is expired so we might attach that table to another.
• then use this data to call driver to renew his license.

Select statement.

• it allow me to make a query on database and bring it.
• query refer to the data i am looking at.
• I can make a query on 1 column, multi columns or the entire table.
• we can think of table as instance like Dog, Bird, Car and so on.
• it means the table contain all properties related to that entity.
• Syntax: ``` SELECT column1, column2 from TABLENAME // i can also select the entire table using (*)

SEECT * from TABLE

#### Queries with constraints
 * sometimes we need to make a query on tables have thousands of rows.
 * and it's pain in the ass to get all rows and search on what we want.
 * constrains allow me to query on table based on condtions.
 * row that satisfy condition will be in result only.
 * SYNTAX: 

SELECT column1, columns2 from TABLE WHERE condition AND/OR condtion two … ```