Read: 08 SQL [sources taken from Complete SQLBolt & SQL Cheat Sheet] - cindyweiss/seattle-301d55 GitHub Wiki

SQL, or Structured Query Language, is a language designed to allow both technical and non-technical users query, manipulate, and transform data from a relational database. And due to its simplicity, SQL databases provide safe and scalable storage for millions of websites and mobile applications.

EXAMPLES OF SQL:

CREATE DATABASE database_name Create a database CREATE DATABASE My_First_Database

DROP DATABASE database_name Delete a database DROP DATABASE My_First_Database

Data Types:

Data Type Description integer(size) Hold integers only. The maximum number of digits are specified in parenthesis. char(size) Holds a fixed length string (can contain letters, numbers, and special characters). The fixed size is specified in parenthesis. varchar(size) Holds a variable length string (can contain letters, numbers, and special characters). The maximum size is specified in parenthesis. date(yyyymmdd) Holds a date

Index Manipulation

CREATE INDEX index_name ON table_name (column_name_1, column_name_2, ...) Create a simple index. CREATE INDEX PersonIndex ON Person (LastName, FirstName)

CREATE UNIQUE INDEX index_name ON table_name (column_name_1, column_name_2, ...) Create a unique index. CREATE UNIQUE INDEX PersonIndex ON Person (LastName DESC)

DROP INDEX table_name.index_name Delete a index. DROP INDEX Person.PersonIndex

Data Manipulation

INSERT INTO table_name VALUES (value_1, value_2,....) Insert new rows into a table. INSERT INTO Persons VALUES('Hussein', 'Saddam', 'White House')

INSERT INTO table_name (column1, column2,...) VALUES (value_1, value_2,....) INSERT INTO Persons (LastName, FirstName, Address) VALUES('Hussein', 'Saddam', 'White House')

UPDATE table_name SET column_name_1 = new_value_1, column_name_2 = new_value_2 WHERE column_name = some_value Update one or several columns in rows. UPDATE Person SET Address = 'ups' WHERE LastName = 'Hussein'

DELETE FROM table_name WHERE column_name = some_value Delete rows in a table. DELETE FROM Person WHERE LastName = 'Hussein'

TRUNCATE TABLE table_name Deletes the data inside the table. TRUNCATE TABLE Person

Select

SELECT column_name(s) FROM table_name Select data from a table. SELECT LastName, FirstName FROM Persons

SELECT * FROM table_name Select all data from a table. SELECT * FROM Persons

SELECT DISTINCT column_name(s) FROM table_name Select only distinct (different) data from a table. SELECT DISTINCT LastName, FirstName FROM Persons

SELECT column_name(s) FROM table_name WHERE column operator value AND column operator value OR column operator value AND (... OR ...) ... Select only certain data from a table. SELECT * FROM Persons WHERE sex='female'