95 lines
1.9 KiB
Markdown
95 lines
1.9 KiB
Markdown
---
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title: "sql"
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tags: [ "Documentation", "data" ]
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---
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MySQL, Aurora and the Maria Database work similarly, and mostly with the same commands.
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MySQL requires 160 Megs of disk space.
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The ontological layers go:
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> Database > table > record > field
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The record is a line containing multiple fields. The table contains multiple records.
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## Database: RPGs
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### Table: D&D
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#### Columns:
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| id | name | year | edition | stars |
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|:--:|:-------------------|:-----|:--------|:------|
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| 1 | Dungeons & Dragons | 1975 | 1 | 1 |
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| 2 | Dungeons & Dragons | 1980 | 2 | 1 |
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| 3 | Advanced Dungeons & Dragons | 1985 | 1 | 1 |
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# Getting started
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> sudo apt-get install mysql-server
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You'll be asked for a password.
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Log in with:
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> mysql -u root -p
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The -u requests a user, while -p tells it to prompt for a password.
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List all databases:
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> show databases;
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Make a new database;
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> create database creatures;
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Start work on the new database:
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> use creatures;
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> create table stats (Strength VARCHAR(2), Speed VARCHAR(2), Dexterity(2));
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This creatures a row called 'stats' within the 'creature'table' with a number of variables, all of type VARCHAR (a variable length character string).
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Now you can insert data (which would normally be provided by a user via php or some-such).
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> insert into stats (Strength,Speed,Dexterity) values (-1,0,+1)
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Now have a look at the info:
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> select * from stats
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The old way to delete info by selection was:
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> delete * from stats where Charisma='0'
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...but now it's:
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> delete from stats where Charisma='0'
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Update a thing:
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> update stats
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> set Speed='-1',Charisma='-2'
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> where Strength=0;
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Leaving out the specifier 'where' means you're updating the entire database.
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Control order with
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> SELECT * FROM stats ORDER BY Strength;
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Or for descending order, suffix 'DESC'.
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> select * from stats ORDER by Date DESC;
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# Resources
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Try more at [w3schools](http://www.w3schools.com/sql/sql_groupby.asp).
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