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# SQL Databases

SQL - Structured Query Language

SQL operates through simple, declarative statements. This keeps data accurate and secure, and helps maintain the integrity of databases, regardless of size.

https://www.codecademy.com/articles/sql-commands

MariaDBKnowledgeBase (opens new window)

# List of SQL Commands

  • Easy Language
  • not case sensitive

https://www.codecademy.com/articles/sql-commands (opens new window)

# Formatting convention

  • Capitalizing commands is a convention that makes queries easier to read
  • columns are named in lower case, and use underscores instead of spaces.
  • The table name itself also uses underscores instead of spaces (it's annoying to deal with spaces in SQL - but it's posiible)
  • putting double quotes around a word or phrase will indicate that you are referring to that column name.

# Statements

A statement is text that the database recognizes as a valid command. Statements always end in a semicolon ;.

CREATE TABLE table_name (
   column_1 data_type, 
   column_2 data_type, 
   column_3 data_type
);
  1. CREATE TABLE is a clause. Clauses perform specific tasks in SQL. By convention, clauses are written in capital letters.
  2. table_name refers to the name of the table that the command is applied to.
  3. (column_1 data_type, column_2 data_type, column_3 data_type) is a parameter. A parameter is a list of columns, data types, or values that are passed to a clause as an argument.

A statement can be written all on one line, or split up across multiple lines if it makes it easier to read.

# Basic Commands

# Comment

  • # comment in SQL
  • s multiple lines using /* to begin the comment and */ to close it

# Create a Database

To create a new database, use this command:

CREATE DATABASE testDB;

In general, the syntax is like this:

 CREATE DATABASE DatabaseName;

You can write all SQL statements in lowercase as well. Convention: use uppercase, so that you see better which words are SQL keywords.

# Show Databases

Show all databases:

SHOW DATABASES;

# Select a Database

Select a database to work with:

USE test;

# Show Selected Database

Show which database is selected:

SELECT database();

# Delete Database

This cannot be reversed!

DROP DATABASE bufg;

← SQL Tables →