A subquery is a query nested inside another query. Subqueries are useful to data practitioners for scaling and making more powerful queries. The main reason we have subqueries is the need to combine information from multiple tables. Information in a relational database isn’t stored in a single table; it’s shared between several tables.
In this course, you’ll learn various types of subqueries, how to use them, and why they are so valuable: scalar subquery, multi-rows subquery and multi-columns subquery. You’ll also learn how to write common table expressions in SQL.
Best of all, you’ll learn by doing — you’ll practice and get feedback directly in the browser.
- Nesting a query inside another query
- Employing different types of subqueries
- Employing common table expressions
- Scaling your project with complex queries
SQL Subqueries [5 lessons]
Scalar Subqueries in SQL 1hLesson Objectives
- Extract a single value from a subquery
- Employ a single value subquery in your queries
- Identify why subqueries are useful
Multi-row and Multi-column Subqueries in SQL 1hLesson Objectives
- Extract multiple rows from a subquery
- Extract multiple columns from a subquery
- Scale your project with multi-row subqueries
Nested and Correlated Subqueries in SQL 1hLesson Objectives
- Nest a subquery inside another subquery
- Write dependent subqueries
- Write effective queries
Common Table Expression in SQL 1hLesson Objectives
- Write Common Table Expressions (CTEs)
- Write Recursive Common Table Expression
Guided Project: Customers and Products Analysis Using SQL 1hLesson Objectives
- Expand your portfolio using real-world data
Projects in this course
Guided Project: Customers and Products Analysis Using SQL
Work on a real-life project using SQL
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