Add table of contents for GitHub

Author: AndreKunitz

README.md

@@ -2,7 +2,71 @@
 
 This repository is a quick personal reference to using Postgres and elaborating SQL queries.
 
-[TOC]
+- [SQL and Postgres Quick Reference](#sql-and-postgres-quick-reference)
+  - [Installing Postgres with Docker](#installing-postgres-with-docker)
+    - [Pull image](#pull-image)
+    - [Start Postgres instance](#start-postgres-instance)
+    - [Bash into instance](#bash-into-instance)
+    - [Login with root superuser access](#login-with-root-superuser-access)
+    - [Crate a new database](#crate-a-new-database)
+    - [Alternative: Connect <em>psql</em> to docker container (needs <em>pqsl/postgres</em> installed locally)](#alternative-connect-psql-to-docker-container-needs-pqslpostgres-installed-locally)
+  - [Postgres Cheat Sheet](#postgres-cheat-sheet)
+  - [Hands-on SQL](#hands-on-sql)
+    - [Creating a database](#creating-a-database)
+    - [Connecting to databases](#connecting-to-databases)
+    - [Create a table without constraints](#create-a-table-without-constraints)
+    - [Drop table](#drop-table)
+    - [Create table with constraints](#create-table-with-constraints)
+    - [Insert data](#insert-data)
+    - [Selects](#selects)
+    - [Adding data](#adding-data)
+    - [Sorting](#sorting)
+    - [Remove duplicates](#remove-duplicates)
+    - [Where clause](#where-clause)
+    - [Limit, Offset and Fetch](#limit-offset-and-fetch)
+    - [In](#in)
+    - [Between](#between)
+    - [Like](#like)
+    - [Group by](#group-by)
+    - [Having](#having)
+    - [Union](#union)
+    - [Union all](#union-all)
+    - [Except and Intersect](#except-and-intersect)
+  - [Aggregate functions](#aggregate-functions)
+    - [Max, Min, Avg](#max-min-avg)
+    - [Sum](#sum)
+  - [Arithmetic Operators](#arithmetic-operators)
+    - [Working with Arithmetic Operators](#working-with-arithmetic-operators)
+  - [Alias](#alias)
+  - [Null handling](#null-handling)
+    - [Coalesce](#coalesce)
+    - [Null if](#null-if)
+  - [Dates](#dates)
+    - [Adding &amp; Subtracting Dates](#adding--subtracting-dates)
+    - [Extracting Fields From Dates](#extracting-fields-from-dates)
+    - [tableAge function](#tableage-function)
+  - [DDL - Data Definition Language](#ddl---data-definition-language)
+    - [Create, Alter and Drop](#create-alter-and-drop)
+    - [Primary Key Constraint](#primary-key-constraint)
+    - [Unique Constraint](#unique-constraint)
+    - [Check Constraint](#check-constraint)
+  - [DML - Data Manipulation Language](#dml---data-manipulation-language)
+    - [Selecting records](#selecting-records)
+    - [Inserting Records](#inserting-records)
+    - [Deleting Records](#deleting-records)
+    - [Updating Records](#updating-records)
+    - [On Conflict Do Nothing](#on-conflict-do-nothing)
+    - [On Conflict Do Update](#on-conflict-do-update)
+  - [Relationships (Foreign Keys &amp; Joins)](#relationships-foreign-keys--joins)
+    - [Updating Foreign Keys](#updating-foreign-keys)
+    - [Inner Joins](#inner-joins)
+    - [Left Joins](#left-joins)
+    - [Deleting Foreign Keys](#deleting-foreign-keys)
+  - [Sequences](#sequences)
+  - [Extensions](#extensions)
+    - [Using UUIDs](#using-uuids)
+  - [Exporting to CSV](#exporting-to-csv)
+  - [References](#references)
 
 ## Installing Postgres with Docker
 
@@ -30,8 +94,6 @@ This repository is a quick personal reference to using Postgres and elaborating
 
 `$ psql -h localhost -p 5432 -U postgres`
 
-
-
 ## Postgres Cheat Sheet
 
 | Action                                       | PostgreSQL command    |
@@ -50,8 +112,6 @@ This repository is a quick personal reference to using Postgres and elaborating
 
 [Link to complete Postgres Cheat Sheet](https://postgrescheatsheet.com/#/tables)
 
-
-
 ## Hands-on SQL
 
 ### Creating a database
@@ -116,8 +176,8 @@ At this stage, we will create fake date to interact with the database e create s
 - For the purpose of this training, we can import data for the _person_ table: [person.sql file](/person.sql)
 
 - To execute a SQL script file in Postgres, we can use the `\i` command:
-  
-  ​	`$ \i ~/Desktop/person.sql`
+
+  ​ `$ \i ~/Desktop/person.sql`
 
 ### Sorting
 
@@ -158,17 +218,17 @@ SELECT * FROM person OFFSET 5 FETCH FIRST 1 ROW ONLY;
 SELECT * FROM person OFFSET 5 FETCH FIRST ROW ONLY;
 ```
 
-### In 
+### In
 
 Array of values and returns results matching these values
 
 ```sql
 SELECT * FROM person
-	WHERE country_of_birth IN ('Brazil', 'China', 'France', 'Mexico') 
+	WHERE country_of_birth IN ('Brazil', 'China', 'France', 'Mexico')
 	ORDER BY country_of_birth;
 ```
 
-### Between 
+### Between
 
 Selects data from a range
 
@@ -177,9 +237,9 @@ SELECT * FROM person
 	WHERE date_of_birth BETWEEN DATE '2000-01-01' AND '2022-01-01';
 ```
 
-### Like 
+### Like
 
-An underscore (`_`) in *`pattern`* stands for (matches) any single character; a percent sign (`%`) matches any sequence of zero or more characters.
+An underscore (`_`) in _`pattern`_ stands for (matches) any single character; a percent sign (`%`) matches any sequence of zero or more characters.
 
 ```sql
 SELECT * FROM person WHERE email LIKE '%@google.%';
@@ -195,7 +255,7 @@ SELECT * FROM person WHERE country_of_birth ILIKE 'p%';
 
 ```sql
 SELECT country_of_birth, COUNT(*) FROM person
-	GROUP BY country_of_birth 
+	GROUP BY country_of_birth
 	ORDER BY country_of_birth;
 ```
 
@@ -204,9 +264,9 @@ SELECT country_of_birth, COUNT(*) FROM person
 Specifies a search condition for a group.
 
 ```sql
-SELECT country_of_birth, COUNT(*) FROM person 
-	GROUP BY country_of_birth 
-	HAVING COUNT(*) > 5 
+SELECT country_of_birth, COUNT(*) FROM person
+	GROUP BY country_of_birth
+	HAVING COUNT(*) > 5
 	ORDER BY country_of_birth;
 ```
 
@@ -236,8 +296,6 @@ SELECT column_name(s) FROM table2;
 
 ### Except and Intersect
 
-
-
 ## Aggregate functions
 
 [Link to aggregate functions](https://www.postgresql.org/docs/9.5/functions-aggregate.html)
@@ -259,8 +317,6 @@ SELECT SUM(price) FROM car;
 SELECT make, SUM(price) FROM car GROUP BY make;
 ```
 
-
-
 ## Arithmetic Operators
 
 ```sql
@@ -276,22 +332,18 @@ SELECT 10 % 4;
 SELECT make, model, price, ROUND(price * .10, 2),  ROUND((price - price * .10), 2) FROM car;
 ```
 
-
-
 ## Alias
 
 ```sql
-SELECT 
-	make, 
-	model, 
+SELECT
+	make,
+	model,
 	price AS original_price,
     ROUND(price * .10, 2) AS ten_percent,
     ROUND((price - price * .10), 2) AS discount_after_ten_percent
 FROM car;
 ```
 
-
-
 ## Null handling
 
 ### Coalesce
@@ -320,8 +372,6 @@ SELECT NULLIF(10, 20);
 SELECT COALESCE(10 / NULLIF(0, 0), 0);
 ```
 
-
-
 ## Dates
 
 [Date and Time types](https://www.postgresql.org/docs/current/datatype-datetime.html)
@@ -356,9 +406,7 @@ SELECT first_name, last_name, date_of_birth, AGE(NOW(), date_of_birth) AS age FR
 -- then extract fields from dates
 ```
 
-
-
-## DDL - Data Definition Language 
+## DDL - Data Definition Language
 
 ### Create, Alter and Drop
 
@@ -377,7 +425,7 @@ CREATE TABLE contacts(
    email VARCHAR(100),
    PRIMARY KEY(contact_id),
    CONSTRAINT fk_customer
-      FOREIGN KEY(customer_id) 
+      FOREIGN KEY(customer_id)
 	  REFERENCES customers(customer_id)
 );
 ```
@@ -394,7 +442,7 @@ ALTER TABLE table_name ADD column_name datatype;
 -- Remove column from table
 ALTER TABLE table_name DROP COLUMN column_name;
 
--- Change column data type 
+-- Change column data type
 ALTER TABLE table_name ALTER COLUMN column_name datatype;
 ```
 
@@ -425,8 +473,6 @@ Check constraint allow us only to add a string that matches the argument.
 ALTER TABLE person ADD CONSTRAINT gender_constraint CHECK (gender == 'Female' OR 'Male');
 ```
 
-
-
 ## DML - Data Manipulation Language
 
 ### Selecting records
@@ -440,7 +486,7 @@ SELECT column1, column2, ... FROM table_name;
 ```sql
 INSERT INTO person (first_name, last_name, gender, email, date_of_birth, country_of_birth)
 	VALUES ('John', 'Doe', 'Male', '[email protected]', DATE '1960-01-01', 'Canada');
-	
+
 -- Multirow insert
 INSERT INTO table_name (column_list)
 VALUES
@@ -454,7 +500,7 @@ VALUES
 
 ```sql
 -- BE CAREFUL: Deletes every record in the table
-DELETE FROM person; 
+DELETE FROM person;
 
 -- Selectively deletes record
 DELETE FROM person WHERE id = 1;
@@ -469,13 +515,13 @@ UPDATE person SET email = '[email protected]';
 -- Selectively deletes record
 UPDATE person SET email = '[email protected]' WHERE id = 1;
 
--- Update multiple columns 
+-- Update multiple columns
 UPDATE person SET email = '[email protected]', name = 'John Doe' WHERE id = 1;
 ```
 
 ### On Conflict Do Nothing
 
-Handle errors. To use it, column must be a primary key or have a unique constraint.  
+Handle errors. To use it, column must be a primary key or have a unique constraint.
 
 ```sql
 INSERT INTO person (id, first_name, last_name, gender, email, date_of_birth, country_of_birth)
@@ -489,24 +535,22 @@ INSERT INTO person (id, first_name, last_name, gender, email, date_of_birth, cou
 
 ### On Conflict Do Update
 
-In this case, we want to update certain fields if the insert encounters an error. 
+In this case, we want to update certain fields if the insert encounters an error.
 
 ```sql
 -- email refers to the current email and EXCLUDED.email refers to the one inste de VALUES array
 INSERT INTO person (id, first_name, last_name, gender, email, date_of_birth, country_of_birth)
 	VALUES (1, 'John', 'Doe', 'Male', '[email protected]', DATE '1960-01-01', 'Canada')
-	ON CONFLICT (id) DO UPDATE SET email = EXCLUDED.email; 
+	ON CONFLICT (id) DO UPDATE SET email = EXCLUDED.email;
 
 INSERT INTO person (id, first_name, last_name, gender, email, date_of_birth, country_of_birth)
 	VALUES (1, 'John', 'Doe', 'Male', '[email protected]', DATE '1960-01-01', 'Canada')
-	ON CONFLICT (id) DO UPDATE SET email = EXCLUDED.email, first_name = EXCLUDED.first_name; 
+	ON CONFLICT (id) DO UPDATE SET email = EXCLUDED.email, first_name = EXCLUDED.first_name;
 ```
 
+## Relationships (Foreign Keys & Joins)
 
-
-##  Relationships (Foreign Keys & Joins)
-
-To follow along, remove the current data and recreate tables and date using the given script. 
+To follow along, remove the current data and recreate tables and date using the given script.
 
 ```sql
 DROP TABLE person;
@@ -531,10 +575,10 @@ Links two tables where primary key and the foreign key is found in both tables.
 
 ```sql
 SELECT * FROM person
-JOIN car ON person.car_id = car.id; 
+JOIN car ON person.car_id = car.id;
 
 SELECT person.first_name, car.make, car.model FROM person
-JOIN car ON person.car_id = car.id; 
+JOIN car ON person.car_id = car.id;
 ```
 
 ### Left Joins
@@ -543,11 +587,11 @@ Links two tables including records that don't have a foreign key relationship (a
 
 ```sql
 SELECT * FROM person
-LEFT JOIN car ON person.car_id = car.id; 
+LEFT JOIN car ON person.car_id = car.id;
 
 SELECT * FROM person
 LEFT JOIN car ON person.car_id = car.id
-WHERE car.* IS NULL; 
+WHERE car.* IS NULL;
 ```
 
 ### Deleting Foreign Keys
@@ -557,8 +601,6 @@ DELETE FROM person WHERE id = 1;
 DELETE FROM car WHERE id = 2;
 ```
 
-
-
 ## Sequences
 
 ```sql
@@ -571,16 +613,14 @@ ALTER SEQUENCE person_id_seq RESTART WITH 10;
 SELECT * FROM person_id_seq;
 ```
 
-
-
 ## Extensions
 
 ```sql
 SELECT * FROM pg_available_extensions ORDER BY name;
 
 CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
 
-SELECT uuid_generate_v4(); 
+SELECT uuid_generate_v4();
 ```
 
 ### Using UUIDs
@@ -596,17 +636,12 @@ SELECT * FROM person LEFT JOIN car USING (car_uid);
 SELECT * FROM person LEFT JOIN car USING (car_uid) WHERE car.* IS NULL;
 ```
 
-
-
 ## Exporting to CSV
 
 ```sql
 \copy (SELECT * FROM person LEFT JOIN car ON person.car_uid = car.car_uid;) TO '~/Desktop/results.csv' DELIMITER ',' CSV HEADER;
 ```
 
-
-
 ## References
 
 The content of this repository was based on [this](https://www.youtube.com/watch?v=5hzZtqCNQKk) course and some personal research.
-