Write Complex Subqueries in SQL
subqueries are essential for performing complex filtering, aggregation, and comparisons that go beyond the capabilities of basic SQL JOIN. They allow queries to be nested inside other que...
Before writing complex subqueries, it is crucial to understand the two main types: non-correlated subqueries and correlated subqueries.
A non-correlated subquery is a subquery that executes independently of the main query. It acts as a temporary dataset whose result is calculated once, then reused for each row of the external query.
Conceptual example: Calculate the total number of orders in the system and display this constant value next to each customer.
Sign in to read this course
A free account unlocks all 514 courses. 20 are readable without one.
What's inside
10 sections- 1 Table of Contents
- 2 Introduction to complex subqueries
- 3 The two basic types of subqueries
- 4 Demo: Filtering and comparison with correlated subqueries
- 5 Demo: Subqueries in the SELECT clause
- 6 Demo: Subqueries in the FROM clause
- 7 Demo: Subqueries in the WHERE clause
- 8 Comparison of subqueries according to SQL platforms
- 9 Key Takeaways
- 10 Demo files
More SQL Fundamentals courses
View all 4Introduction to SQL
SQL is different from other programming languages — and that's precisely what makes it so valuable.
Perform Complex JOINS in SQL
This course covers the execution of complex JOINs in SQL. It is aimed at people who already master the fundamentals of SQL JOINs and wish to deepen their knowledge with advanced technique...
Simplify SQL Queries with Common Table Expressions (CTEs)
A CTE (Common Table Expression) is a temporary result set that can be used inside a SELECT, INSERT, UPDATE or DELETE query. CTEs are comparable to subqueries, but with increased flexibility.
Interested in this course?
Contact us to book it or get a custom training plan for your team.