This document provides an overview of SQL concepts including installing MySQL, data types, data definition and manipulation statements, filtering, sorting, aggregation, and join operations. It covers downloading and installing MySQL, describes common data types like numeric, date/time, and string types. It also explains how to create databases and tables, add/update/delete data, and perform queries with WHERE, ORDER BY, LIMIT, and JOIN clauses.

1. Crash course in SQL
www.skewcode.com

2. MySQL - Installation
DOWNLOAD
○ https://dev.mysql.com/downloads
■ MySQL Community Server
■ MySQL Shell
■ [OPTIONAL] MySQL Workbench
○ https://dev.mysql.com/doc/index-other.html
■ Example databases -> world database

3. Data Types
Data types
● Numeric types (INT, DECIMAL, FLOAT, DOUBLE, BIT)
● Date & Time types (DATE, TIME, DATETIME, TIMESTAMP)
● String types (CHAR, VARCHAR, TEXT, ENUM)

4. Data Definition Statements
Database related operations
List all databases SHOW DATABASES;
Create a new database. CREATE DATABASE mydb1;
Create a new database (if not existing). CREATE DATABASE IF NOT EXISTS mydb1;
Use an existing database. USE mydb1;
List current database. SELECT DATABASE();
Delete existing database. DROP DATABASE mydb1;
Delete existing database (if existing). DROP DATABASE IF EXISTS mydb1;

5. Data Definition Statements
Table related operations
List all tables in current database SHOW TABLES;
See structure of a specific table. DESCRIBE mytable1;
Create a new table (if not existing). CREATE TABLE IF NOT EXISTS mytable1
(
serialnum INT,
name VARCHAR(20),
location ENUM(‘BLR’, ‘BOM’, ‘DEL’)
);
Delete existing table (if existing). DROP TABLE IF EXISTS mytable1;

6. Data Definition Statements
Table related operations
Adding columns. ALTER TABLE mytable1
ADD COLUMN firstname varchar(25),
ADD COLUMN lastname varchar(40);
Deleting columns. ALTER TABLE mytable1
DROP COLUMN firstname,
DROP COLUMN lastname;
Modifying columns. ALTER TABLE mytable1
MODIFY COLUMN firstname varchar(25),
MODIFY COLUMN lastname varchar(40);

7. Data Definition Statements
Constraints
NOT NULL CREATE TABLE mytable1 (col1 INT NOT NULL);
PRIMARY KEY CREATE TABLE mytable1 (col1 INT, PRIMARY KEY (col1));
UNIQUE CREATE TABLE mytable1 (col1 INT UNIQUE);
FOREIGN KEY CREATE TABLE mytable1
(
col1 INT, FOREIGN KEY(col1) REFERENCES mytable2(mycol)
);
DEFAULT CREATE TABLE mytable1 (col1 INT DEFAULT 100);

8. Data Manipulation Statements
Adding, deleting and updating data (rows)
Add a new row (data in all
columns).
INSERT INTO mytable1
VALUES (‘10’, ‘mithun’, ‘shanbhag’);
Add a new row (data in
specific columns).
INSERT INTO mytable1 (firstname, lastname)
VALUES (‘mithun’, ‘shanbhag’);
Update row(s). UPDATE mytable1
SET firstname = ‘sachin’, lastname = ‘tendulkar’
WHERE serialnum = 101;
Delete row(s). DELETE FROM mytable1
WHERE firstname = ‘mithun’;
Delete all row(s). DELETE * FROM mytable1;

9. Data Query Statements
● Data Query Statements
○ Filtering Operations (WHERE)
○ Sorting Operations (ORDER BY)
○ Set Operations (DISTINCT, UNION, UNION ALL)
○ Paging Operations (LIMIT)
○ Aliasing Operations (AS)
○ Aggregation Operations (MIN, MAX, AVERAGE, SUM, COUNT)
○ Grouping Operations (GROUP BY)
○ Join Operations (JOIN)

10. Data Query Statements
Filtering Operations (WHERE)
Extract cities in USA. SELECT *
FROM city
WHERE countrycode = ’usa’;
Extract cities in USA with
population greater than
1,000,000.
SELECT *
FROM city
WHERE countrycode = ’usa’ AND population >
1000000;
Extract cities in USA or
cities with population
greater than 1,000,000.
SELECT *
FROM city
WHERE countrycode = ‘usa’ OR population > 1000000;

11. Data Query Statements
Filtering Operations (WHERE)
Extract countries starting
with ‘B’.
SELECT *
FROM country
WHERE name LIKE ’b%’;
Extract countries starting
with ‘B’ and ending with ‘a’.
SELECT *
FROM country
WHERE name LIKE ’b%a’;
Extract countries which
have 5 letters in their
name.
SELECT *
FROM country
WHERE name LIKE ’_____’;

12. Data Query Statements
Filtering Operations (WHERE)
Extract countries with no
head of state.
SELECT *
FROM country
WHERE headofstate IS NULL;
Extract countries which
have heads of state.
SELECT *
FROM country
WHERE headofstate IS NOT NULL;
Extract countries
beginning from letter ‘W’
onwards.
SELECT *
FROM country
WHERE name > ’w’;
Extract countries with
population between
10,000 and 20,000.
SELECT *
FROM country
WHERE population BETWEEN 10000 AND 20000;

13. Data Query Statements
Sorting Operations (ORDER BY)
Sort countries by name. SELECT *
FROM country
ORDER BY name;
Sort countries by population (descending). SELECT *
FROM country
ORDER BY population DESC;
Sort countries by continent, then by
population (descending).
SELECT *
FROM country
ORDER BY continent, population DESC;

14. Data Query Statements
Set Operations (DISTINCT)
Extract unique continent names SELECT DISTINCT continent
FROM country;
Extract unique countrycode and district
combinations
SELECT DISTINCT countrycode, district
FROM city;

15. Data Query Statements
Set Operations (UNION)
● Combines the result-set of two or more SELECT statements.
● Each SELECT statement must have the same number of columns, with ‘similar’ data types and in the
same order.
● UNION supports only ‘distinct’ values, however UNION ALL allows duplicates.
Combine the list of country codes from
the ‘city’ and ‘countrylanguage’ tables.
SELECT countrycode FROM city
UNION
SELECT countrycode FROM countrylanguage
ORDER BY countrycode;

16. Data Query Statements
Paging Operations (LIMIT)
● Constrain the number of rows returned in result set.
Extract top 5 countries, sorted by
population.
SELECT *
FROM country
ORDER BY population DESC
LIMIT 5;
Extract countries 6 to 10, sorted by
population.
SELECT *
FROM country
ORDER BY population DESC
LIMIT 5, 5;

17. Data Query Statements
Aliasing Operations (AS)
● Gives a table (or column) a temporary, readable name (alias).
● The alias exists only for the duration of the query.
Aliasing a column name. SELECT name AS cityname, population
FROM country
WHERE cityname = ‘new york’;
Aliasing a table name. SELECT name, population
FROM country as c
WHERE c.name = ‘new york’;

18. Data Query Statements
Aggregation Operations (MIN, MAX, AVG, SUM, COUNT)
Least population. SELECT MIN(population)
FROM country;
Most population. SELECT MAX(population)
FROM country;
Average population. SELECT AVG(population)
FROM country;
Total population. SELECT SUM(population)
FROM country;
Total number of countries. SELECT COUNT(name)
FROM country;

19. Data Query Statements
Grouping Operations (GROUP BY)
● Groups the result set using a ‘key’.
● The GROUP BY statement is often used with aggregate functions (COUNT, MAX, MIN, SUM, AVG).
Find number of countries in each continent. SELECT continent, count(name)
FROM country
GROUP BY continent;
Group Swedish districts by total
population.
SELECT district, sum(population)
FROM city
WHERE countrycode = ‘swe’
GROUP BY district;

20. Data Query Statements
Join Operations
INNER JOIN LEFT OUTER
JOIN
RIGHT OUTER
JOIN
FULL OUTER
JOIN

21. Data Query Statements
Inner Join
Display continent
information for cities.
SELECT id, city.name, countrycode, district, continent
FROM city
INNER JOIN country ON city.CountryCode = country.code;

22. References
● https://dev.mysql.com/doc/refman/5.7/en/
● https://www.w3schools.com/sql/default.asp