What is Subquery in SQL?
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Chapters:
00:06 - What is a Subquery in SQL?
00:12 - Understanding Subqueries and Their Uses in SQL
00:18 - How Subqueries Work with Outer Queries in SQL
00:24 - Subqueries in SELECT, FROM, WHERE, and HAVING Clauses in SQL
00:31 - Placement and Usage of Subqueries in SQL
00:40 - Simplifying Complex Queries with Subqueries in SQL
00:46 - Differences Between Subqueries and Common Table Expressions (CTEs) in SQL
00:51 - When to Use Common Table Expressions in SQL
00:58 - Comparison of Subqueries and CTEs in SQL
01:04 - The Complexity of Queries Using Subqueries in SQL
01:09 - Challenges in Reading and Modifying Subqueries in SQL
01:14 - Benefits of Using Common Table Expressions
01:20 - Practical Example of Subqueries
01:28 - Sample Table and Query Setup
01:34 - Writing and Testing Subqueries
01:40 - Selecting Maximum Values with Subqueries in SQL
01:52 - Creating and Using a Subquery for Max Value in SQL
02:12 - Query Execution and Output Analysis
02:24 - Recommendations for Simplified Queries
02:34 - Using CTEs for Better Query Management
02:41 - Final Thoughts on Subqueries vs. CTEs in SQL
We'll discuss subqueries, which are queries embedded within another query. Subqueries are used for data analysis and manipulation, and their results can be used in SELECT, FROM, WHERE, or HAVING clauses. While both subqueries and Common Table Expressions (CTEs) serve similar purposes, CTEs are generally preferred for their simplicity and readability. Understanding subqueries is important for interviews.
In a practical example, we demonstrated finding the maximum sales unit value using a subquery. Although CTEs can achieve the same result more clearly, subqueries are useful to know.
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15 сен 2024
