SQL SERVER – How to Write Correlated Subquery?

This is a follow-up blog post to my earlier blog post written about SQL SERVER – Writing Your First Subquery From a Single Table. In the blog post, we discuss how to write a correlated subquery and why it is actually necessary. In a query, a correlated subquery is a subquery that uses values from the outer query. Subqueries are usually running once for each row processed for outer query and that is why they are often inefficient as well.

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How to Create an Empty Table and Fool Optimizer to Believe It Contains Data? – Interview Question of the Week #204

Question: How to Create an Empty Table and Fool Optimizer to Believe It Contains Data?

Answer: Before I answer this question, I must acknowledge that I have never heard this question in my 20 years career before and I must ask you back, where do you come up with these kinds of questions.

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