Ecosyste.ms: Awesome
An open API service indexing awesome lists of open source software.
https://github.com/lifeparticle/MySQL-Snippets
⌗ Learn MySQL.
https://github.com/lifeparticle/MySQL-Snippets
data database docker docker-compose mysql mysql-database sql table
Last synced: 6 days ago
JSON representation
⌗ Learn MySQL.
- Host: GitHub
- URL: https://github.com/lifeparticle/MySQL-Snippets
- Owner: lifeparticle
- License: mit
- Created: 2020-02-07T13:14:27.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2024-03-16T02:14:51.000Z (8 months ago)
- Last Synced: 2024-08-01T10:19:19.065Z (3 months ago)
- Topics: data, database, docker, docker-compose, mysql, mysql-database, sql, table
- Homepage:
- Size: 96.7 KB
- Stars: 20
- Watchers: 3
- Forks: 25
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
[How to Run MySQL Using Docker](https://towardsdatascience.com/how-to-run-mysql-using-docker-ed4cebcd90e4?source=friends_link&sk=2ec5b230e4c0bcffd485b9a3d924d64a)
[How to Run MySQL and phpMyAdmin Using Docker](https://towardsdatascience.com/how-to-run-mysql-and-phpmyadmin-using-docker-17dfe107eab7?source=friends_link&sk=f94fbd748334e2fab7351c7b4446911a)
* [SQL](#sql)
* [MySQL](#mysql)
* [Docker Setup](#docker-setup)
* [MySQL Keywords](#mysql-keywords)
* [MySQL Databases](#mysql-databases)
* [MySQL Tables](#mysql-tables)
* [SELECT with AND](#select-with-and)
* [SELECT multiple fields](#select-multiple-fields)
* [SELECT with DISTINCT and MOD](#select-with-distinct-and-mod)
* [Count duplicates](#count-duplicates)
* [Find the shortest and longest strings ordered alphabetically](#find-the-shortest-and-longest-strings-ordered-alphabetically)
* [Find unique strings that starts with vowels](#find-unique-strings-that-starts-with-vowels)
* [Find unique strings that ends with vowels](#find-unique-strings-that-ends-with-vowels)
* [Find unique strings that starts or ends with vowels](#find-unique-strings-that-starts-or-ends-with-vowels)
* [Find unique strings that does not starts with vowels](#find-unique-strings-that-does-not-starts-with-vowels)
* [Find unique strings that does not ends with vowels](#find-unique-strings-that-does-not-ends-with-vowels)
* [Find unique strings that does not starts or ends with vowels](#find-unique-strings-that-does-not-starts-or-ends-with-vowels)
* [Find unique strings that does not starts and ends with vowels](#find-unique-strings-that-does-not-starts-and-ends-with-vowels)
* [LEFT and RIGHT](#left-and-right)
* [Ascending order](#ascending-order)
* [GROUP BY, GROUP_CONCAT, FLOOR, AVG with JOIN](#group-by-group_concat-floor-avg-with-join)
* [IF with JOIN](#if-with-join)
* [BETWEEN with JOIN](#between-with-join)
* [Joining tables](#joining-tables)
* [INNER JOIN](#inner-join)
* [OUTER JOIN](#outer-join)
* [LEFT JOIN](#left-join)
* [RIGHT JOIN](#right-join)
* [FULL OUTER JOIN](#full-outer-join)
* [CASE](#case)
* [COUNT(*)](#count)
* [ROUND](#round)
* [MIN and MAX](#min-and-max)
* [REPLACE](#replace)
* [LIMIT](#limit)
* [Find duplicates](#find-duplicates)
* [IN](#in)
* [Like](#like)
* [Output query results to a file](#output-query-results-to-a-file)
* [Miscellaneous](#miscellaneous)
* [Resources](#resources)
# SQL
SQL, "sequel"; Structured Query Language) is a domain-specific language used in programming and designed for managing data held in a relational database management system (RDBMS), or for stream processing in a relational data stream management system (RDSMS). It is particularly useful in handling structured data, i.e. data incorporating relations among entities and variables.
# MySQL
MySQL is an open-source relational database management system (RDBMS).
# Docker Setup
Run the following command from the same directory, where the docker-compose.yml file is located.
```bash
docker-compose up
```
access the running container `mysql-snippets_db_1`
```bash
docker exec -it mysql-snippets_db_1 bash
```
# MySQL Keywords
[Keywords](https://dev.mysql.com/doc/refman/8.0/en/keywords.html)
# Data types
| No | Name | Example | Doc |
| --- | ------------- | ------- | --------- |
| 1 | Numeric | | [link][1] |
| 2 | Date and Time | | [link][2] |
| 3 | String | | [link][3] |
| 5 | Spatial | | [link][4] |
| 6 | JSON | | [link][5] |
[1]: https://dev.mysql.com/doc/refman/8.0/en/numeric-types.html
[2]: https://dev.mysql.com/doc/refman/8.0/en/date-and-time-types.html
[3]: https://dev.mysql.com/doc/refman/8.0/en/string-types.html
[4]: https://dev.mysql.com/doc/refman/8.0/en/spatial-types.html
[5]: https://dev.mysql.com/doc/refman/8.0/en/json.html
# MySQL Databases
Run the MySQl queries from this file [students.sql](students.sql) from the MySQL CLI.
```mysql
mysql -uroot -proot
```
or import the sql file.
```mysql
mysql -uroot -p test_db < school.sql
```
Type the password `root` and you're done.
```mysql
SHOW DATABASES;
USE test_db;
```
```mysql
SELECT * FROM students;
```
Create a new database.
```mysql
CREATE DATABASE test_db_1;
```
Delete a database. This will delete all the tables within the database.
```mysql
DROP DATABASE test_db_1;
```
# MySQL Tables
Show all tables in a database.
```mysql
SHOW TABLES;
```
```mysql
+-------------------+
| Tables_in_test_db |
+-------------------+
| marks |
| students |
+-------------------+
2 rows in set (0.00 sec)
```
Delete a table. If you don't have a storage issue, it's best practise that you rename the table and after few weeks later when you are sure that there are no issues, then you can delete the table.
```mysql
DROP TABLE table_name;
```
Rename a table. Be aware that one or more application can be using the old table name
```mysql
RENAME TABLE old_table_name TO new_table_name;
```
Copy a table.
```mysql
CREATE TABLE new_table_name TO old_table_name;
INSERT new_table_name SELECT * FROM old_table_name;
```
## SELECT with AND
```mysql
SELECT * FROM students WHERE first_name='Bob' and postcode=23031;
```
```mysql
+----+------------+----------------+----------------+------------------+--------+-----------------------+---------------------------------------------------------+----------+---------------+
| id | first_name | last_name | city | phone | gender | email | address | postcode | date_of_birth |
+----+------------+----------------+----------------+------------------+--------+-----------------------+---------------------------------------------------------+----------+---------------+
| 5 | Bob | Schulistland | Schulistland | 895-877-0076x197 | Male | [email protected] | 39405 Nicolas Walk Apt. 041 Kozeychester, AL 20566-8063 | 23031 | 2019-07-15 |
| 16 | Bob | Port Thoraland | Port Thoraland | 1-628-108-7615 | Male | [email protected] | 9256 Price Summit Garrickland, KY 23867 | 23031 | 2016-02-05 |
+----+------------+----------------+----------------+------------------+--------+-----------------------+---------------------------------------------------------+----------+---------------+
2 rows in set (0.00 sec)
```
## SELECT multiple fields
```mysql
SELECT city, postcode FROM students;
```
```mysql
+---------------------+----------+
| city | postcode |
+---------------------+----------+
| Rathmouth | 23031 |
| Port Lolamouth | 27108 |
| Lavernastad | 76631 |
| Ethelville | 37965 |
| Schulistland | 23031 |
| Kennithside | 23031 |
| Oberbrunnerchester | 24772 |
| Marcoport | 16 |
| New Adalineton | 89650 |
| East Kayla | 45934 |
| Kevinmouth | 7820 |
| North Deondreland | 32292 |
| Port Adrianaborough | 55848 |
| South Hunter | 29257 |
| East Breanne | 49701 |
| Port Thoraland | 23031 |
| West Jedediahville | 80323 |
| Franeckiland | 39741 |
| Lake Clare | 24982 |
| Beattyburgh | 7864 |
| Oberbrunnerport | 36356 |
| Ricofort | 69978 |
| East Graycefurt | 49614 |
| West Joeport | 16353 |
| Oceanestad | 70534 |
| Creolashire | 58634 |
| North Ernestinaton | 90902 |
| Jakaylaland | 10160 |
| North Esta | 40221 |
| West Breanabury | 23031 |
+---------------------+----------+
30 rows in set (0.00 sec)
```
## SELECT with DISTINCT and MOD
```mysql
SELECT DISTINCT first_name FROM students WHERE MOD(postcode, 2) = 0;
```
```mysql
+------------+
| first_name |
+------------+
| Hounson |
| Blewmen |
| Vanacci |
| Marflitt |
| Pietesch |
| Henrique |
| Tynan |
| Pinkard |
| Whale |
| Ori |
| Tagg |
| Costerd |
| Corrin |
| Lumley |
| Whiles |
| Presdee |
| Bedberry |
+------------+
17 rows in set (0.00 sec)
```
## Count duplicates
```mysql
SELECT (COUNT(postcode)-COUNT(DISTINCT(postcode))) FROM students;
```
```
+---------------------------------------------+
| (COUNT(postcode)-COUNT(DISTINCT(postcode))) |
+---------------------------------------------+
| 4 |
+---------------------------------------------+
1 row in set (0.00 sec)
```
## Find the shortest and longest strings ordered alphabetically
```mysql
SELECT first_name, LENGTH(first_name) FROM students ORDER BY LENGTH(first_name) DESC, first_name ASC LIMIT 1;
```
```mysql
+-------------+--------------------+
| first_name | LENGTH(first_name) |
+-------------+--------------------+
| Whaplington | 11 |
+-------------+--------------------+
1 row in set (0.00 sec)
```
```mysql
SELECT first_name, LENGTH(first_name) FROM students ORDER BY LENGTH(first_name) ASC, first_name ASC LIMIT 1;
```
```mysql
+------------+--------------------+
| first_name | LENGTH(first_name) |
+------------+--------------------+
| Bob | 3 |
+------------+--------------------+
1 row in set (0.00 sec)
```
## Find unique strings that starts with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name REGEXP '^[aeiou]';
```
```mysql
+------------+
| first_name |
+------------+
| Ailn |
| Ori |
+------------+
2 rows in set (0.01 sec)
```
## Find unique strings that ends with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name REGEXP '[aeiou]$';
```
```mysql
+------------+
| first_name |
+------------+
| Vanacci |
| Henrique |
| Leeke |
| Whale |
| Ori |
| Presdee |
+------------+
6 rows in set (0.00 sec)
```
## Find unique strings that starts or ends with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name REGEXP '^[aeiou].*[aeiou]$';
```
```mysql
+------------+
| first_name |
+------------+
| Ori |
+------------+
1 row in set (0.00 sec)
```
## Find unique strings that does not starts with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name NOT REGEXP '^[aeiou]';
```
```mysql
+-------------+
| first_name |
+-------------+
| Hounson |
| Tison |
| Surmeyers |
| Bob |
| Holdey |
| Blewmen |
| Vanacci |
| Marflitt |
| Pietesch |
| Henrique |
| Tynan |
| Pinkard |
| Haslock |
| Rickell |
| Boxhill |
| Leeke |
| Whale |
| Tagg |
| Costerd |
| Corrin |
| Bunford |
| Lumley |
| Whiles |
| Presdee |
| Bedberry |
| Danilchev |
| Whaplington |
+-------------+
27 rows in set (0.00 sec)
```
## Find unique strings that does not ends with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name NOT REGEXP '[aeiou]$';
```
```mysql
+-------------+
| first_name |
+-------------+
| Ailn |
| Hounson |
| Tison |
| Surmeyers |
| Bob |
| Holdey |
| Blewmen |
| Marflitt |
| Pietesch |
| Tynan |
| Pinkard |
| Haslock |
| Rickell |
| Boxhill |
| Tagg |
| Costerd |
| Corrin |
| Bunford |
| Lumley |
| Whiles |
| Bedberry |
| Danilchev |
| Whaplington |
+-------------+
23 rows in set (0.01 sec)
```
## Find unique strings that does not starts or ends with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name NOT REGEXP '^[aeiou].*[aeiou]$';
```
```mysql
+-------------+
| first_name |
+-------------+
| Ailn |
| Hounson |
| Tison |
| Surmeyers |
| Bob |
| Holdey |
| Blewmen |
| Vanacci |
| Marflitt |
| Pietesch |
| Henrique |
| Tynan |
| Pinkard |
| Haslock |
| Rickell |
| Boxhill |
| Leeke |
| Whale |
| Tagg |
| Costerd |
| Corrin |
| Bunford |
| Lumley |
| Whiles |
| Presdee |
| Bedberry |
| Danilchev |
| Whaplington |
+-------------+
28 rows in set (0.00 sec)
```
## Find unique strings that does not starts and ends with vowels
```mysql
SELECT DISTINCT first_name FROM students WHERE first_name NOT REGEXP '^[aeiou]' AND first_name NOT REGEXP '[aeiou]$';
```
```mysql
+-------------+
| first_name |
+-------------+
| Hounson |
| Tison |
| Surmeyers |
| Bob |
| Holdey |
| Blewmen |
| Marflitt |
| Pietesch |
| Tynan |
| Pinkard |
| Haslock |
| Rickell |
| Boxhill |
| Tagg |
| Costerd |
| Corrin |
| Bunford |
| Lumley |
| Whiles |
| Bedberry |
| Danilchev |
| Whaplington |
+-------------+
22 rows in set (0.00 sec)
```
## LEFT and RIGHT
```mysql
SELECT first_name, LEFT(first_name, 3), RIGHT(first_name, 3) FROM students;
```
```mysql
+-------------+---------------------+----------------------+
| first_name | LEFT(first_name, 3) | RIGHT(first_name, 3) |
+-------------+---------------------+----------------------+
| Ailn | Ail | iln |
| Hounson | Hou | son |
| Tison | Tis | son |
| Surmeyers | Sur | ers |
| Bob | Bob | Bob |
| Holdey | Hol | dey |
| Blewmen | Ble | men |
| Vanacci | Van | cci |
| Marflitt | Mar | itt |
| Pietesch | Pie | sch |
| Henrique | Hen | que |
| Tynan | Tyn | nan |
| Pinkard | Pin | ard |
| Haslock | Has | ock |
| Rickell | Ric | ell |
| Bob | Bob | Bob |
| Boxhill | Box | ill |
| Leeke | Lee | eke |
| Whale | Wha | ale |
| Ori | Ori | Ori |
| Tagg | Tag | agg |
| Costerd | Cos | erd |
| Corrin | Cor | rin |
| Bunford | Bun | ord |
| Lumley | Lum | ley |
| Whiles | Whi | les |
| Presdee | Pre | dee |
| Bedberry | Bed | rry |
| Danilchev | Dan | hev |
| Whaplington | Wha | ton |
+-------------+---------------------+----------------------+
30 rows in set (0.00 sec)
```
## Ascending order
```mysql
SELECT first_name from students ORDER BY first_name ASC;
```
```mysql
+-------------+
| first_name |
+-------------+
| Ailn |
| Bedberry |
| Blewmen |
| Bob |
| Bob |
| Boxhill |
| Bunford |
| Corrin |
| Costerd |
| Danilchev |
| Haslock |
| Henrique |
| Holdey |
| Hounson |
| Leeke |
| Lumley |
| Marflitt |
| Ori |
| Pietesch |
| Pinkard |
| Presdee |
| Rickell |
| Surmeyers |
| Tagg |
| Tison |
| Tynan |
| Vanacci |
| Whale |
| Whaplington |
| Whiles |
+-------------+
30 rows in set (0.00 sec)
```
## GROUP BY, GROUP_CONCAT, FLOOR, AVG with JOIN
```mysql
SELECT students.id, students.first_name, students.last_name, FLOOR(AVG(marks.mark)), GROUP_CONCAT(marks.subject) FROM students JOIN marks
ON students.id = marks.student_id
GROUP BY students.id;
```
```mysql
+----+------------+--------------------+------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| id | first_name | last_name | FLOOR(AVG(marks.mark)) | GROUP_CONCAT(marks.subject) |
+----+------------+--------------------+------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| 1 | Ailn | Rathmouth | 85 | Alien Ethics,Foreign Arts,Space Travel,Alien Dance History,Planetary Ecology |
| 2 | Hounson | Port Lolamouth | 52 | Mathematics,Planetary History |
| 3 | Tison | Lavernastad | 63 | Magic Survival,Foreign Ethics,Foreign Statistics,Foreign Pathology,Galactic History |
| 4 | Surmeyers | Ethelville | 71 | Necromancy,Dimensional Manipulation,Nutrition Recognition,Transmutation,Planetary Geography,Alien Economics,Magic Music,Magic Rituals,Foreign Instrumental Music |
| 5 | Bob | Schulistland | 76 | Alien Medicine |
| 6 | Holdey | Kennithside | 57 | Alien Physiology,Alien Social Studies,Magic Music,Intergallactic Relations,Herbalism,Foreign Arts |
| 7 | Blewmen | Oberbrunnerchester | 75 | Foreign Political Sciences,Military Law,Alien Bioengineering,Foreign Social Skills,Foreign History |
| 8 | Vanacci | Marcoport | 64 | Foreign Services,Alien Social Skills,Alien Genealogy,Terraforming |
| 9 | Marflitt | New Adalineton | 48 | Grand Strategy,Magic Arts,Foreign Evolutionary Biology |
+----+------------+--------------------+------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------+
9 rows in set (0.00 sec)
```
## IF with JOIN
```mysql
SELECT students.id, IF(marks.mark < 50, "Fail", "Pass"), marks.subject AS result FROM students JOIN marks
ON students.id = marks.student_id;
```
```mysql
+----+-------------------------------------+------------------------------+
| id | IF(marks.mark < 50, "Fail", "Pass") | result |
+----+-------------------------------------+------------------------------+
| 3 | Fail | Magic Survival |
| 4 | Pass | Planetary Geography |
| 9 | Pass | Foreign Evolutionary Biology |
| 6 | Pass | Intergallactic Relations |
| 9 | Fail | Grand Strategy |
| 7 | Pass | Foreign History |
| 1 | Pass | Alien Dance History |
| 7 | Pass | Foreign Social Skills |
| 8 | Pass | Alien Social Skills |
| 4 | Pass | Magic Music |
| 8 | Pass | Alien Genealogy |
| 4 | Pass | Magic Rituals |
| 1 | Pass | Planetary Ecology |
| 7 | Pass | Military Law |
| 3 | Pass | Foreign Ethics |
| 4 | Pass | Foreign Instrumental Music |
| 8 | Pass | Foreign Services |
| 4 | Pass | Alien Economics |
| 1 | Pass | Alien Ethics |
| 9 | Fail | Magic Arts |
| 6 | Fail | Alien Social Studies |
| 7 | Pass | Foreign Political Sciences |
| 8 | Pass | Terraforming |
| 4 | Pass | Transmutation |
| 1 | Pass | Space Travel |
| 5 | Pass | Alien Medicine |
| 3 | Pass | Foreign Statistics |
| 4 | Pass | Necromancy |
| 6 | Fail | Magic Music |
| 2 | Fail | Planetary History |
| 6 | Pass | Herbalism |
| 4 | Fail | Dimensional Manipulation |
| 4 | Pass | Nutrition Recognition |
| 3 | Pass | Foreign Pathology |
| 6 | Pass | Foreign Arts |
| 7 | Pass | Alien Bioengineering |
| 6 | Pass | Alien Physiology |
| 2 | Pass | Mathematics |
| 1 | Pass | Foreign Arts |
| 3 | Pass | Galactic History |
+----+-------------------------------------+------------------------------+
40 rows in set (0.01 sec)
```
## BETWEEN with JOIN
```mysql
SELECT students.id, marks.mark, marks.subject FROM students JOIN marks
ON students.id = marks.student_id
WHERE marks.mark BETWEEN 90 AND 100;
```
```mysql
+----+------+---------------------+
| id | mark | subject |
+----+------+---------------------+
| 1 | 98 | Alien Dance History |
| 4 | 91 | Alien Economics |
| 1 | 91 | Alien Ethics |
| 1 | 98 | Space Travel |
| 3 | 98 | Foreign Statistics |
| 4 | 100 | Necromancy |
+----+------+---------------------+
6 rows in set (0.00 sec)
```
## Joining tables
### INNER JOIN
In MySQL, `JOIN`, `CROSS JOIN`, and `INNER JOIN` are syntactic equivalents (they can replace each other).
An inner join will give you all common rows in both A and B.
```mysql
SELECT s.first_name, s.last_name, m.mark
FROM students AS s JOIN marks AS m
ON m.student_id = s.id
ORDER BY m.mark;
```
```mysql
+------------+--------------------+------+
| first_name | last_name | mark |
+------------+--------------------+------+
| Holdey | Kennithside | 0 |
| Tison | Lavernastad | 23 |
| Marflitt | New Adalineton | 23 |
| Surmeyers | Ethelville | 34 |
| Hounson | Port Lolamouth | 34 |
| Holdey | Kennithside | 34 |
| Marflitt | New Adalineton | 45 |
| Blewmen | Oberbrunnerchester | 54 |
| Surmeyers | Ethelville | 56 |
| Tison | Lavernastad | 56 |
| Vanacci | Marcoport | 56 |
| Surmeyers | Ethelville | 56 |
| Tison | Lavernastad | 57 |
| Holdey | Kennithside | 58 |
| Vanacci | Marcoport | 59 |
| Vanacci | Marcoport | 65 |
| Surmeyers | Ethelville | 67 |
| Ailn | Rathmouth | 69 |
| Hounson | Port Lolamouth | 71 |
| Ailn | Rathmouth | 72 |
| Blewmen | Oberbrunnerchester | 76 |
| Vanacci | Marcoport | 76 |
| Surmeyers | Ethelville | 76 |
| Surmeyers | Ethelville | 76 |
| Bob | Schulistland | 76 |
| Marflitt | New Adalineton | 77 |
| Blewmen | Oberbrunnerchester | 79 |
| Blewmen | Oberbrunnerchester | 80 |
| Holdey | Kennithside | 81 |
| Holdey | Kennithside | 83 |
| Tison | Lavernastad | 84 |
| Blewmen | Oberbrunnerchester | 87 |
| Holdey | Kennithside | 88 |
| Surmeyers | Ethelville | 89 |
| Ailn | Rathmouth | 91 |
| Surmeyers | Ethelville | 91 |
| Ailn | Rathmouth | 98 |
| Tison | Lavernastad | 98 |
| Ailn | Rathmouth | 98 |
| Surmeyers | Ethelville | 100 |
+------------+--------------------+------+
40 rows in set (0.00 sec)
```
### OUTER JOIN
#### LEFT JOIN
A left outer join will give all rows in A, plus any common rows in B.
```mysql
SELECT s.first_name, s.last_name, m.mark FROM students AS s
LEFT JOIN marks AS m ON m.student_id = s.id
ORDER BY m.mark;
```
```mysql
+-------------+---------------------+------+
| first_name | last_name | mark |
+-------------+---------------------+------+
| Whaplington | West Breanabury | NULL |
| Boxhill | West Jedediahville | NULL |
| Bob | Port Thoraland | NULL |
| Rickell | East Breanne | NULL |
| Haslock | South Hunter | NULL |
| Pinkard | Port Adrianaborough | NULL |
| Tynan | North Deondreland | NULL |
| Henrique | Kevinmouth | NULL |
| Pietesch | East Kayla | NULL |
| Leeke | Franeckiland | NULL |
| Whale | Lake Clare | NULL |
| Ori | Beattyburgh | NULL |
| Tagg | Oberbrunnerport | NULL |
| Costerd | Ricofort | NULL |
| Corrin | East Graycefurt | NULL |
| Bunford | West Joeport | NULL |
| Presdee | North Ernestinaton | NULL |
| Lumley | Oceanestad | NULL |
| Danilchev | North Esta | NULL |
| Bedberry | Jakaylaland | NULL |
| Whiles | Creolashire | NULL |
| Holdey | Kennithside | 0 |
| Marflitt | New Adalineton | 23 |
| Tison | Lavernastad | 23 |
| Hounson | Port Lolamouth | 34 |
| Surmeyers | Ethelville | 34 |
| Holdey | Kennithside | 34 |
| Marflitt | New Adalineton | 45 |
| Blewmen | Oberbrunnerchester | 54 |
| Vanacci | Marcoport | 56 |
| Surmeyers | Ethelville | 56 |
| Tison | Lavernastad | 56 |
| Surmeyers | Ethelville | 56 |
| Tison | Lavernastad | 57 |
| Holdey | Kennithside | 58 |
| Vanacci | Marcoport | 59 |
| Vanacci | Marcoport | 65 |
| Surmeyers | Ethelville | 67 |
| Ailn | Rathmouth | 69 |
| Hounson | Port Lolamouth | 71 |
| Ailn | Rathmouth | 72 |
| Blewmen | Oberbrunnerchester | 76 |
| Vanacci | Marcoport | 76 |
| Surmeyers | Ethelville | 76 |
| Bob | Schulistland | 76 |
| Surmeyers | Ethelville | 76 |
| Marflitt | New Adalineton | 77 |
| Blewmen | Oberbrunnerchester | 79 |
| Blewmen | Oberbrunnerchester | 80 |
| Holdey | Kennithside | 81 |
| Holdey | Kennithside | 83 |
| Tison | Lavernastad | 84 |
| Blewmen | Oberbrunnerchester | 87 |
| Holdey | Kennithside | 88 |
| Surmeyers | Ethelville | 89 |
| Surmeyers | Ethelville | 91 |
| Ailn | Rathmouth | 91 |
| Tison | Lavernastad | 98 |
| Ailn | Rathmouth | 98 |
| Ailn | Rathmouth | 98 |
| Surmeyers | Ethelville | 100 |
+-------------+---------------------+------+
61 rows in set (0.00 sec)
```
#### RIGHT JOIN
A right outer join will give all rows in B, plus any common rows in A.
```mysql
SELECT s.first_name, s.last_name, m.mark FROM students AS s
RIGHT JOIN marks AS m ON m.student_id = s.id
ORDER BY m.mark;
```
```mysql
+------------+--------------------+------+
| first_name | last_name | mark |
+------------+--------------------+------+
| Holdey | Kennithside | 0 |
| Tison | Lavernastad | 23 |
| Marflitt | New Adalineton | 23 |
| Surmeyers | Ethelville | 34 |
| Hounson | Port Lolamouth | 34 |
| Holdey | Kennithside | 34 |
| Marflitt | New Adalineton | 45 |
| Blewmen | Oberbrunnerchester | 54 |
| Surmeyers | Ethelville | 56 |
| Tison | Lavernastad | 56 |
| Vanacci | Marcoport | 56 |
| Surmeyers | Ethelville | 56 |
| Tison | Lavernastad | 57 |
| Holdey | Kennithside | 58 |
| Vanacci | Marcoport | 59 |
| Vanacci | Marcoport | 65 |
| Surmeyers | Ethelville | 67 |
| Ailn | Rathmouth | 69 |
| Hounson | Port Lolamouth | 71 |
| Ailn | Rathmouth | 72 |
| Blewmen | Oberbrunnerchester | 76 |
| Vanacci | Marcoport | 76 |
| Surmeyers | Ethelville | 76 |
| Surmeyers | Ethelville | 76 |
| Bob | Schulistland | 76 |
| Marflitt | New Adalineton | 77 |
| Blewmen | Oberbrunnerchester | 79 |
| Blewmen | Oberbrunnerchester | 80 |
| Holdey | Kennithside | 81 |
| Holdey | Kennithside | 83 |
| Tison | Lavernastad | 84 |
| NULL | NULL | 84 |
| Blewmen | Oberbrunnerchester | 87 |
| Holdey | Kennithside | 88 |
| Surmeyers | Ethelville | 89 |
| Ailn | Rathmouth | 91 |
| Surmeyers | Ethelville | 91 |
| Ailn | Rathmouth | 98 |
| Tison | Lavernastad | 98 |
| Ailn | Rathmouth | 98 |
| Surmeyers | Ethelville | 100 |
+------------+--------------------+------+
41 rows in set (0.00 sec)
```
#### FULL OUTER JOIN
A full outer join will give you all the rows in A and all the rows in B. We can use the follwing code to emulate full outer joins.
```mysql
SELECT s.first_name, s.last_name, m.mark FROM students AS s
LEFT JOIN marks AS m ON m.student_id = s.id
UNION ALL
SELECT s.first_name, s.last_name, m.mark FROM students AS s
RIGHT JOIN marks AS m ON m.student_id = s.id
WHERE s.id is null;
```
```mysql
+-------------+---------------------+------+
| first_name | last_name | mark |
+-------------+---------------------+------+
| Ailn | Rathmouth | 72 |
| Ailn | Rathmouth | 98 |
| Ailn | Rathmouth | 91 |
| Ailn | Rathmouth | 69 |
| Ailn | Rathmouth | 98 |
| Hounson | Port Lolamouth | 71 |
| Hounson | Port Lolamouth | 34 |
| Tison | Lavernastad | 84 |
| Tison | Lavernastad | 56 |
| Tison | Lavernastad | 98 |
| Tison | Lavernastad | 57 |
| Tison | Lavernastad | 23 |
| Surmeyers | Ethelville | 67 |
| Surmeyers | Ethelville | 34 |
| Surmeyers | Ethelville | 100 |
| Surmeyers | Ethelville | 76 |
| Surmeyers | Ethelville | 91 |
| Surmeyers | Ethelville | 56 |
| Surmeyers | Ethelville | 89 |
| Surmeyers | Ethelville | 76 |
| Surmeyers | Ethelville | 56 |
| Bob | Schulistland | 76 |
| Holdey | Kennithside | 81 |
| Holdey | Kennithside | 88 |
| Holdey | Kennithside | 58 |
| Holdey | Kennithside | 0 |
| Holdey | Kennithside | 34 |
| Holdey | Kennithside | 83 |
| Blewmen | Oberbrunnerchester | 80 |
| Blewmen | Oberbrunnerchester | 54 |
| Blewmen | Oberbrunnerchester | 79 |
| Blewmen | Oberbrunnerchester | 87 |
| Blewmen | Oberbrunnerchester | 76 |
| Vanacci | Marcoport | 56 |
| Vanacci | Marcoport | 59 |
| Vanacci | Marcoport | 76 |
| Vanacci | Marcoport | 65 |
| Marflitt | New Adalineton | 23 |
| Marflitt | New Adalineton | 45 |
| Marflitt | New Adalineton | 77 |
| Pietesch | East Kayla | NULL |
| Henrique | Kevinmouth | NULL |
| Tynan | North Deondreland | NULL |
| Pinkard | Port Adrianaborough | NULL |
| Haslock | South Hunter | NULL |
| Rickell | East Breanne | NULL |
| Bob | Port Thoraland | NULL |
| Boxhill | West Jedediahville | NULL |
| Leeke | Franeckiland | NULL |
| Whale | Lake Clare | NULL |
| Ori | Beattyburgh | NULL |
| Tagg | Oberbrunnerport | NULL |
| Costerd | Ricofort | NULL |
| Corrin | East Graycefurt | NULL |
| Bunford | West Joeport | NULL |
| Lumley | Oceanestad | NULL |
| Whiles | Creolashire | NULL |
| Presdee | North Ernestinaton | NULL |
| Bedberry | Jakaylaland | NULL |
| Danilchev | North Esta | NULL |
| Whaplington | West Breanabury | NULL |
| NULL | NULL | 84 |
+-------------+---------------------+------+
62 rows in set (0.00 sec)
```
## CASE
```mysql
SELECT
CASE
WHEN marks.mark >= 90 AND marks.mark <= 100 THEN "A"
WHEN marks.mark >= 80 AND marks.mark <= 89 THEN "B"
WHEN marks.mark >= 70 AND marks.mark <= 79 THEN "C"
WHEN marks.mark >= 60 AND marks.mark <= 69 THEN "D"
WHEN marks.mark >= 50 AND marks.mark <= 59 THEN "E"
ELSE "F"
END AS grades
FROM marks
ORDER BY grades;
```
```mysql
+--------+
| grades |
+--------+
| A |
| A |
| A |
| A |
| A |
| A |
| B |
| B |
| B |
| B |
| B |
| B |
| B |
| B |
| C |
| C |
| C |
| C |
| C |
| C |
| C |
| C |
| C |
| D |
| D |
| D |
| E |
| E |
| E |
| E |
| E |
| E |
| E |
| E |
| F |
| F |
| F |
| F |
| F |
| F |
| F |
+--------+
41 rows in set (0.00 sec)
```
```mysql
SELECT marks.mark,
CASE
WHEN marks.mark >= 90 AND marks.mark <= 100 THEN "A"
WHEN marks.mark >= 80 AND marks.mark <= 89 THEN "B"
WHEN marks.mark >= 70 AND marks.mark <= 79 THEN "C"
WHEN marks.mark >= 60 AND marks.mark <= 69 THEN "D"
WHEN marks.mark >= 50 AND marks.mark <= 59 THEN "E"
ELSE "F"
END AS grades
FROM marks
ORDER BY grades;
```
```mysql
+------+--------+
| mark | grades |
+------+--------+
| 100 | A |
| 91 | A |
| 91 | A |
| 98 | A |
| 98 | A |
| 98 | A |
| 84 | B |
| 81 | B |
| 80 | B |
| 88 | B |
| 89 | B |
| 87 | B |
| 84 | B |
| 83 | B |
| 76 | C |
| 76 | C |
| 72 | C |
| 71 | C |
| 79 | C |
| 76 | C |
| 76 | C |
| 76 | C |
| 77 | C |
| 69 | D |
| 67 | D |
| 65 | D |
| 56 | E |
| 56 | E |
| 58 | E |
| 56 | E |
| 54 | E |
| 59 | E |
| 56 | E |
| 57 | E |
| 34 | F |
| 0 | F |
| 34 | F |
| 34 | F |
| 23 | F |
| 45 | F |
| 23 | F |
+------+--------+
41 rows in set (0.00 sec)
```
```mysql
SELECT students.id, marks.mark, marks.subject,
CASE
WHEN marks.mark >= 90 AND marks.mark <= 100 THEN "A"
WHEN marks.mark >= 80 AND marks.mark <= 89 THEN "B"
WHEN marks.mark >= 70 AND marks.mark <= 79 THEN "C"
WHEN marks.mark >= 60 AND marks.mark <= 69 THEN "D"
WHEN marks.mark >= 50 AND marks.mark <= 59 THEN "E"
ELSE "F"
END AS grades
FROM students
JOIN marks ON students.id = marks.student_id
ORDER BY grades;
```
```mysql
+----+------+------------------------------+--------+
| id | mark | subject | grades |
+----+------+------------------------------+--------+
| 4 | 100 | Necromancy | A |
| 4 | 91 | Alien Economics | A |
| 1 | 91 | Alien Ethics | A |
| 3 | 98 | Foreign Statistics | A |
| 1 | 98 | Alien Dance History | A |
| 1 | 98 | Space Travel | A |
| 6 | 81 | Alien Physiology | B |
| 7 | 80 | Alien Bioengineering | B |
| 6 | 88 | Foreign Arts | B |
| 4 | 89 | Magic Rituals | B |
| 7 | 87 | Foreign Social Skills | B |
| 3 | 84 | Galactic History | B |
| 6 | 83 | Intergallactic Relations | B |
| 4 | 76 | Transmutation | C |
| 5 | 76 | Alien Medicine | C |
| 1 | 72 | Foreign Arts | C |
| 2 | 71 | Mathematics | C |
| 7 | 79 | Military Law | C |
| 8 | 76 | Alien Genealogy | C |
| 4 | 76 | Magic Music | C |
| 7 | 76 | Foreign History | C |
| 9 | 77 | Foreign Evolutionary Biology | C |
| 1 | 69 | Planetary Ecology | D |
| 4 | 67 | Nutrition Recognition | D |
| 8 | 65 | Alien Social Skills | D |
| 4 | 56 | Planetary Geography | E |
| 3 | 56 | Foreign Pathology | E |
| 6 | 58 | Herbalism | E |
| 8 | 56 | Terraforming | E |
| 7 | 54 | Foreign Political Sciences | E |
| 8 | 59 | Foreign Services | E |
| 4 | 56 | Foreign Instrumental Music | E |
| 3 | 57 | Foreign Ethics | E |
| 2 | 34 | Planetary History | F |
| 6 | 0 | Magic Music | F |
| 4 | 34 | Dimensional Manipulation | F |
| 6 | 34 | Alien Social Studies | F |
| 9 | 23 | Magic Arts | F |
| 9 | 45 | Grand Strategy | F |
| 3 | 23 | Magic Survival | F |
+----+------+------------------------------+--------+
40 rows in set (0.00 sec)
```
## `COUNT(*)`
The `COUNT(*)` function returns the number of rows in a result set returned by a SELECT statement. It returns the number of rows including duplicate, non-NULL and NULL rows.
```mysql
SELECT
CASE
WHEN marks.mark >= 90 AND marks.mark <= 100 THEN "A"
WHEN marks.mark >= 80 AND marks.mark <= 89 THEN "B"
WHEN marks.mark >= 70 AND marks.mark <= 79 THEN "C"
WHEN marks.mark >= 60 AND marks.mark <= 69 THEN "D"
WHEN marks.mark >= 50 AND marks.mark <= 59 THEN "E"
ELSE "F"
END AS grades,
COUNT(*) AS count
FROM students
JOIN marks ON students.id = marks.student_id
GROUP BY grades
ORDER BY grades;
```
```mysql
+--------+-------+
| grades | count |
+--------+-------+
| A | 6 |
| B | 7 |
| C | 9 |
| D | 3 |
| E | 8 |
| F | 7 |
+--------+-------+
6 rows in set (0.00 sec)
```
## ROUND
```mysql
SELECT ROUND(SUM(mark), 2) FROM marks;
```
```mysql
+---------------------+
| ROUND(SUM(mark), 2) |
+---------------------+
| 2777.00 |
+---------------------+
1 row in set (0.00 sec)
```
## MIN and MAX
```mysql
SELECT MAX(mark), MIN(mark) FROM marks;
```
```mysql
+-----------+-----------+
| MAX(mark) | MIN(mark) |
+-----------+-----------+
| 100 | 0 |
+-----------+-----------+
1 row in set (0.00 sec)
```
## REPLACE
```mysql
SELECT subject, REPLACE(subject, 'Magic', 'Sorcery') FROM marks;
```
```mysql
+------------------------------+--------------------------------------+
| subject | REPLACE(subject, 'Magic', 'Sorcery') |
+------------------------------+--------------------------------------+
| Magic Survival | Sorcery Survival |
| Planetary Geography | Planetary Geography |
| Foreign Evolutionary Biology | Foreign Evolutionary Biology |
| Intergallactic Relations | Intergallactic Relations |
| Grand Strategy | Grand Strategy |
| Foreign History | Foreign History |
| Alien Dance History | Alien Dance History |
| Foreign Social Skills | Foreign Social Skills |
| Alien Social Skills | Alien Social Skills |
| Magic Music | Sorcery Music |
| Alien Genealogy | Alien Genealogy |
| Magic Rituals | Sorcery Rituals |
| Planetary Ecology | Planetary Ecology |
| Military Law | Military Law |
| Foreign Ethics | Foreign Ethics |
| Foreign Instrumental Music | Foreign Instrumental Music |
| Foreign Services | Foreign Services |
| Alien Economics | Alien Economics |
| Alien Ethics | Alien Ethics |
| Magic Arts | Sorcery Arts |
| Alien Social Studies | Alien Social Studies |
| Foreign Political Sciences | Foreign Political Sciences |
| Terraforming | Terraforming |
| Transmutation | Transmutation |
| Space Travel | Space Travel |
| Alien Medicine | Alien Medicine |
| Foreign Statistics | Foreign Statistics |
| Necromancy | Necromancy |
| Magic Music | Sorcery Music |
| Planetary History | Planetary History |
| Herbalism | Herbalism |
| Dimensional Manipulation | Dimensional Manipulation |
| Nutrition Recognition | Nutrition Recognition |
| Foreign Pathology | Foreign Pathology |
| Foreign Arts | Foreign Arts |
| Alien Bioengineering | Alien Bioengineering |
| Alien Physiology | Alien Physiology |
| Mathematics | Mathematics |
| Foreign Arts | Foreign Arts |
| Galactic History | Galactic History |
| Galactic History | Galactic History |
+------------------------------+--------------------------------------+
41 rows in set (0.00 sec)
```
## LIMIT
```mysql
SELECT * FROM marks
LIMIT 1;
```
```mysql
+----+------------+------+----------------+
| id | student_id | mark | subject |
+----+------------+------+----------------+
| 1 | 3 | 23 | Magic Survival |
+----+------------+------+----------------+
1 row in set (0.00 sec)
```
LIMIT x, y means return y rows, starting from xth row.
```mysql
SELECT * FROM marks
LIMIT 0, 5;
```
```mysql
+----+------------+------+------------------------------+
| id | student_id | mark | subject |
+----+------------+------+------------------------------+
| 1 | 3 | 23 | Magic Survival |
| 2 | 4 | 56 | Planetary Geography |
| 3 | 9 | 77 | Foreign Evolutionary Biology |
| 4 | 6 | 83 | Intergallactic Relations |
| 5 | 9 | 45 | Grand Strategy |
+----+------------+------+------------------------------+
5 rows in set (0.01 sec)
```
## Find duplicates
```mysql
SELECT subject, count(*) FROM marks
GROUP BY subject
HAVING count(*) > 1;
```
```mysql
+------------------+----------+
| subject | count(*) |
+------------------+----------+
| Magic Music | 2 |
| Foreign Arts | 2 |
| Galactic History | 2 |
+------------------+----------+
3 rows in set (0.00 sec)
```
## IN
```mysql
SELECT * FROM marks
WHERE subject IN ('Magic Music');
```
```mysql
+----+------------+------+-------------+
| id | student_id | mark | subject |
+----+------------+------+-------------+
| 10 | 4 | 76 | Magic Music |
| 29 | 6 | 0 | Magic Music |
+----+------------+------+-------------+
2 rows in set (0.01 sec)
```
## Like
* % - any sequence of zero, one, or multiple characters
* _ - matches a single character
To match `%` or `_` use a backslash as a prefix.
```mysql
SHOW DATABASES LIKE 'test%';
```
```mysql
+------------------+
| Database (test%) |
+------------------+
| test_db |
+------------------+
1 row in set (0.00 sec)
```
```mysql
SHOW DATABASES LIKE 'test\_d_';
```
```mysql
+---------------------+
| Database (test\_d_) |
+---------------------+
| test_db |
+---------------------+
1 row in set (0.00 sec)
```
## Output query results to a file
```mysql
```
```mysql
```
# Miscellaneous
```mysql
SELECT REPEAT('* ', 1);
SELECT REPEAT('* ', 2);
SELECT REPEAT('* ', 3);
SELECT REPEAT('* ', 4);
SELECT REPEAT('* ', 5);
SELECT REPEAT('* ', 6);
SELECT REPEAT('* ', 7);
SELECT REPEAT('* ', 8);
SELECT REPEAT('* ', 9);
SELECT REPEAT('* ', 10);
SELECT REPEAT('* ', 11);
SELECT REPEAT('* ', 12);
SELECT REPEAT('* ', 13);
SELECT REPEAT('* ', 14);
SELECT REPEAT('* ', 15);
SELECT REPEAT('* ', 16);
SELECT REPEAT('* ', 17);
SELECT REPEAT('* ', 18);
SELECT REPEAT('* ', 19);
SELECT REPEAT('* ', 20);
```
```mysql
SELECT elt(locate(operation, "+-*/"), a+b, a-b, a*b, a/b) = c
```
# Resources
1. [SQL](https://en.wikipedia.org/wiki/SQL)
2. [MySQL](https://en.wikipedia.org/wiki/MySQL)
3. [filldb](http://filldb.info/)
4. [mockaroo](https://www.mockaroo.com/)
5. [fantasynamegenerators](https://www.fantasynamegenerators.com/school-subjects.php)
6. [join](https://dev.mysql.com/doc/refman/8.0/en/join.html)
7. [what-is-the-difference-between-inner-join-and-outer-join](https://stackoverflow.com/questions/38549/what-is-the-difference-between-inner-join-and-outer-join)
8. [how-to-write-full-outer-join-in-mysql](https://www.xaprb.com/blog/2006/05/26/how-to-write-full-outer-join-in-mysql)
9. [MySQL Tutorial for Beginners](https://www.youtube.com/watch?v=7S_tz1z_5bA)
10. [COUNT(*)](https://www.mysqltutorial.org/mysql-count/#:~:text=The%20COUNT(*)%20function%20returns,non%2DNULL%20and%20NULL%20rows.)
11. [sql](https://www.hackerrank.com/domains/sql)
12. [Planetscale courses](https://planetscale.com/learn/courses/database-scaling/introduction/course-introduction)
13. [File Space Management](https://dev.mysql.com/doc/refman/8.3/en/innodb-file-space.html)