markdown [MySQL] snippets for mysql #snippets #mysql

Posted 2021-05-06

**Select but without duplicates** 

``` SELECT distinct name, email, acception FROM owners WHERE acception = 1 AND date >= 2015-01-01 00:00:00 ```

**Calculate total number of records**

``` SELECT SUM([column]) FROM [table]; ```

**Count total number of `[column]` and group by `[category-column]`** 

``` SELECT [category-column], SUM([column]) FROM [table] GROUP BY [category-column]; ```

**Get largest value in `[column]`**

``` SELECT MAX([column]) FROM [table]; ```

**Get smallest value** 

``` SELECT MIN([column]) FROM [table]; ```

**Get average value**

``` SELECT AVG([column]) FROM [table]; ```

**Get rounded average value and group by `[category-column]`**

``` SELECT [category-column], ROUND(AVG([column]), 2) FROM [table] GROUP BY [category-column]; ```

**Access monitor** 

 ``` mysql -u [username] -p; ``` 

**Show all databases**

 ``` show databases; ```

**Access database**

``` mysql -u [username] -p [database] ``` (will prompt for password)

**Create new database**

``` create database [database]; ```

**Select database**

``` use [database]; ```

**Determine what database is in use**

``` select database(); ```

**Show all tables**

``` show tables; ```

**Show table structure**

``` describe [table]; ```

**List all indexes on a table**

``` show index from [table]; ```

**Create new table with columns** 

``` CREATE TABLE [table] ([column] VARCHAR(120), [another-column] DATETIME); ```

**Adding a column**

``` ALTER TABLE [table] ADD COLUMN [column] VARCHAR(120); ```

**Adding a column with an unique, auto-incrementing ID** 

``` ALTER TABLE [table] ADD COLUMN [column] int NOT NULL AUTO_INCREMENT PRIMARY KEY; ```

**Inserting a record**

``` INSERT INTO [table] ([column], [column]) VALUES ('[value]', [value]'); ```

**MySQL function for datetime input** 

``` NOW() ```

**Selecting records**

``` SELECT * FROM [table]; ``` 

**Explain records**

``` EXPLAIN SELECT * FROM [table]; ```

**Selecting parts of records**

```SELECT [column], [another-column] FROM [table];```

**Counting records**

``` SELECT COUNT([column]) FROM [table]; ```

**Counting and selecting grouped records**

``` SELECT *, (SELECT COUNT([column]) FROM [table]) AS count FROM [table] GROUP BY [column]; ```

**Selecting specific records  (Selectors: `<`, `>`, `!=`; combine multiple selectors with `AND`, `OR`)**

``` SELECT * FROM [table] WHERE [column] = [value]; ```

**Select records containing** 

``` `[value]`: `SELECT * FROM [table] WHERE [column] LIKE '%[value]%'; ```

**Select records starting with** 

``` `[value]`: `SELECT * FROM [table] WHERE [column] LIKE '[value]%'; ```

**Select records starting with `val` and ending with `ue`** 

```SELECT * FROM [table] WHERE [column] LIKE '[val_ue]'; ```

**Select a range** 

``` SELECT * FROM [table] WHERE [column] BETWEEN [value1] and [value2]; ```

**Select with custom order and only limit** 

``` SELECT * FROM [table] WHERE [column] ORDER BY [column] ASC LIMIT [value];` (Order: `DESC`, `ASC`) ```

**Updating records** 

``` UPDATE [table] SET [column] = '[updated-value]' WHERE [column] = [value]; ```

**Deleting records** 

``` DELETE FROM [table] WHERE [column] = [value]; ```

**Delete `all records` from a table without dropping the table, also resets the incrementing counter for auto generated columns like an id column**

``` DELETE FROM [table]; ```

**Delete all records in a table**

``` truncate table [table]; ```

**Removing table columns**

``` ALTER TABLE [table] DROP COLUMN [column]; ```

**Deleting tables**

``` DROP TABLE [table]; ```

**Deleting databases**

``` DROP DATABASE [database]; ```

**Custom column output names**

``` SELECT [column] AS [custom-column] FROM [table]; ```

**Export a database dump (more info [here](http://stackoverflow.com/a/21091197/1815847))** 
Use `--lock-tables=false` option for locked tables (more info [here](http://stackoverflow.com/a/104628/1815847)).

``` mysqldump -u [username] -p [database] > db_backup.sql ```



**Import a database dump (more info [here](http://stackoverflow.com/a/21091197/1815847))** 

``` mysql -u [username] -p -h localhost [database] < db_backup.sql ```

**Logout**

``` exit;```

**Select from multiple tables**

``` SELECT [table1].[column], [table1].[another-column], [table2].[column] FROM [table1], [table2]; ```

**Combine rows from different tables**

``` SELECT * FROM [table1] INNER JOIN [table2] ON [table1].[column] = [table2].[column]; ```

**Combine rows from different tables but do not require the join condition (The left table is the first table that appears in the statement.)**

``` SELECT * FROM [table1] LEFT OUTER JOIN [table2] ON [table1].[column] = [table2].[column];``` 

**Rename column or table using an _alias_**

``` SELECT [table1].[column] AS '[value]', [table2].[column] AS '[value]' FROM [table1], [table2]; ```

**List all users**

``` SELECT User,Host FROM mysql.user; ```

**Create new user**

``` CREATE USER 'username'@'localhost' IDENTIFIED BY 'password'; ```

**Grant `ALL` access to user for `*` tables**

``` GRANT ALL ON database.* TO 'user'@'localhost'; ```

**Find out the IP Address of the Mysql Host ([source](http://serverfault.com/a/129646))**

``` SHOW VARIABLES WHERE Variable_name = 'hostname'; ``` 

Resources 
----------

Soruce: 
1. [hofmannsven](https://gist.github.com/hofmannsven/9164408)



Getting started: 
- http://www.sqlteaching.com/
- https://www.codecademy.com/courses/learn-sql

Related tutorials:
- [MySQL-CLI](https://www.youtube.com/playlist?list=PLfdtiltiRHWEw4-kRrh1ZZy_3OcQxTn7P)
- [Analyzing Business Metrics](https://www.codecademy.com/learn/sql-analyzing-business-metrics)
- [SQL joins infografic](https://lh4.googleusercontent.com/-RdjzcoAwBYg/UxTXWGJHgoI/AAAAAAAACrs/Gqbu6zyksgo/w852-h670/sql-joins.jpg)

Tools:
- [DataGrip](https://www.jetbrains.com/datagrip/)
- [Sequel Pro](http://www.sequelpro.com/)