I have been working with a lot of SQL lately. I wouldn’t label myself an expert, but I have been finding my way around a lot easier the more I work with it.
I have been working a lot with normalizing data and writing queries that reference multiple tables. When referencing multiple tables, it is common to write a join. Here is a very small overview that explains the difference between Left, Right, Inner and Outer Join:
- Join and Inner Join
- Only show records that are common to both tables. Whether the records are common is determined by the fields in join clause
- Left Join and Left Outer Join
- Show all records from left table regardless of the existance of matching records in the right table.
- Right Join and Right Outer Join
- Show all records from the “RIGHT” table and only matching records from the first or “LEFT” Table.