SQL & Relational Databases

Quick visual reference for relational database queries, join behaviors, set operations, and query structures.

SQL Relational Operations

Core SQL Patterns

Joins Summary

• INNER JOIN: Returns records that have matching values in both tables.
• LEFT (OUTER) JOIN: Returns all records from the left table, and matched records from the right table.
• RIGHT (OUTER) JOIN: Returns all records from the right table, and matched records from the left table.
• FULL (OUTER) JOIN: Returns all records when there is a match in either left or right table.
• CROSS JOIN: Produces the Cartesian product of rows from both tables.

Aggregation & Filtering

Remember the standard SQL clause evaluation order:

1. FROM & JOIN
2. WHERE (row-level filtering before grouping)
3. GROUP BY (aggregations)
4. HAVING (group-level filtering after aggregations)
5. SELECT (projections and expressions)
6. DISTINCT
7. ORDER BY
8. LIMIT / OFFSET