sonalranjit / sql-tutorial

SQL Salon

SQL Tutorial on Thu, May 24, 2018

Summary of topics

1. Data Definition Language
2. Basic Structure
3. Set Operations
4. Aggregate Functions
5. Null Values
6. Nested Subqueries

Likely, we won't cover these topics...

1. Modification of the Database
2. Views
3. Integrity Constraints

Code Examples

We will be using http://sqlfiddle.com to do all exercises, with sample SQL filesall.sql and others in the repo.

Overview

1. Data Definition Language

• create table
• domain types
• timestamps in SQL

See sample SQL files for examples.

More exercises

• SQL Lesson 16: Creating tables https://sqlbolt.com/lesson/creating_tables SQL Lesson 17: Altering tables https://sqlbolt.com/lesson/altering_tables
• SQL Lesson 18: Dropping tables https://sqlbolt.com/lesson/dropping_tables SQL Lesson 13: Inserting rows https://sqlbolt.com/lesson/inserting_rows SQL Lesson 14: Updating rows https://sqlbolt.com/lesson/updating_rows SQL Lesson 15: Deleting rows https://sqlbolt.com/lesson/deleting_rows

2. Basic Structure

• select-from-where

• Movie Examples from movie.sql
  • WHERE clause: can use many different kinds of pattern matching:
    • attribute names of the relation(s) used in the FROM.
    • comparison operators: =, <>, <, >, <=, >=
    • apply arithmetic operations: rating*2
    • operations on strings (e.g., “||” for concatenation).
    • Lexicographic order on strings.
    • Pattern matching: s LIKE p
    • Special stuff for comparing dates and times.
  • Selection & projection
  • Joins
  • DISTINCT
  • Renaming attributes
• New Students Example from students.sql
  • String comparison
  • Ordering of tuples
  • Sorting

More exercises

SQL Lesson 1: SELECT queries 101 https://sqlbolt.com/lesson/select_queries_introduction

SQL Lesson 2: Queries with constraints (Pt. 1) https://sqlbolt.com/lesson/select_queries_with_constraints SQL Lesson 3: Queries with constraints (Pt. 2) https://sqlbolt.com/lesson/select_queries_with_constraints_pt_2 SQL Lesson 4: Filtering and sorting Query results https://sqlbolt.com/lesson/filtering_sorting_query_results

SQL Review: Simple SELECT Queries https://sqlbolt.com/lesson/select_queries_review

3. Set Operations

• union, intersect, except
• SQL exercises using sample files

More exercises

Unions, Intersections & Exceptions https://sqlbolt.com/topic/set_operations

4. Nested Subqueries

• SELECT, FROM, WHERE, HAVING can itself contain SQL query - but WHERE is most common
• MovieStars Example
• EXISTS, NOT EXISTS operations
• try oldest, youngest, etc calculations using nested subqueries first
• skip division query

Exercises

SQL Topic: Subqueries https://sqlbolt.com/topic/subqueries

5. Aggregate Functions

• Avg, Min, Max, Sum, Count
• groupings of your own (Student Example)
• HAVING

More exercises

• SQL Lesson 10: Queries with aggregates (Pt. 1) https://sqlbolt.com/lesson/select_queries_with_aggregates
• SQL Lesson 11: Queries with aggregates (Pt. 2) https://sqlbolt.com/lesson/select_queries_with_aggregates_pt_2

Overall summary:

6. Joins

• SQL Lesson 6: Multi-table queries with JOINs https://sqlbolt.com/lesson/select_queries_with_joins SQL Lesson 7: OUTER JOINs https://sqlbolt.com/lesson/select_queries_with_outer_joins

5. Null Values

• SQL Lesson 8: A short note on NULLs https://sqlbolt.com/lesson/select_queries_with_nulls

Challenge Problems!

Use prof.sql for these problems.

Consider the following collection of relation schemes:

professor(profname, deptname)
department(deptname, building)
committee(commname, profname)

1. Find all the professors who are in any one of the committees that professor Piper is in.

2. Find all the professors who are in at least all those committees that professor Piper is in.

3. Find all the professors who have not offices in any of those buildings that Professor Piper has offices in.

Interactive Tutorials

• SQLZoo http://sqlzoo.net/wiki/SQL_Tutorial

• SQL Teaching https://www.sqlteaching.com

• PostgreSQL Exercises https://pgexercises.com/

• HackerRank problems https://www.hackerrank.com/domains/sql/advanced-join

• SQL for data analysis https://community.modeanalytics.com/sql/tutorial/introduction-to-sql/

• Khan Academy https://www.khanacademy.org/computing/hour-of-code/hour-of-sql/p/creating-a-table-and-inserting-data

• Advanced SQL https://news.ycombinator.com/item?id=13417326