sql-notes's Introduction

SQL Notes

This repository contains a collection of SQL notes and examples that demonstrate my proficiency in using SQL to manipulate and query data. The notes cover a range of topics, including common SQL commands, data types, and database concepts, and are designed to showcase my ability to effectively use SQL in a variety of settings.

Basic SQL

'CREATE TABLE' Statement - Creates a table.
'INSERT INTO' Statement - Inserts records into a database.
'SELECT' and 'FROM' Statements - Selects data from a database.
'WHERE' Statement - Extract only records that fulfill a specified condition.
'GROUP BY' and 'ORDER BY' Statements - Groups rows that have the same values into summary rows. Orders records in specified order.

Intermediate SQL

'JOIN' Statement - Combine rows from two or more tables, based on a related column.
'UNION' Statement - Combine two or more 'SELECT' statements.
'CASE' Statement - Evaluates conditions sequentially, similar to if/then/else.
'HAVING' Statement - Used because 'WHERE' cannot be used with aggregate functions.
'UPDATE' and 'DELETE' Statements - Modifies/Deletes existing records in a table.
'AS' Statement - Aliases give tables or columns temporary names, makes it more readable.
'PARTITION BY' Statement - Divides rows/query result set into small partitons. Similar to 'GROUP BY' except all rows are shown.

Advanced SQL

CTE 'WITH' Statement - Temporary table from a SELECT statement that can be used in a subsequent SELECT statement.
Temp Tables - Database table that exists temporarily on the database server.
Subqueries - Nested SELECT statement within another SELECT, INSERT, UPDATE, or DELETE statement.
'TRIM' Statement - Removes leading or trailing spaces from a string.
'CREATE PROCEDURE' Statement - Stores a precompiled collection of SQL statements in the database.
'ALTER PROCEDURE' Statement - Modifies it.