Join Joey D'Antoni for an in-depth discussion in this video Nested loop vs. hash join, part of SQL Server Performance for Developers.
- [Instructor] Next we're going to talk about nested loop…versus hash joins.…These are two different types of joins…that are options in SQL Server.…And when we say they're options,…they're options to the query optimizer.…You can influence the behavior which you'll see in the demo.…However, typically this isn't something you're going to do…and you're going to let the optimizer make the decision for you…and the optimizer is going to make that decision…based on the number of rows and number of columns…and a number of other factors…that it's estimated into its costing model…to join that data together.…
In particular, we're going to talk about hash joins…and nested loops,…but SQL Server also uses merge joins…in addition to hash and nested loop joins.…What hash joins are is a table that gets created in memory…to match values together…and bring them together for your join operation.…Hash joins are very efficient on a large set of data.…They're less efficient on a very small set of data…because the process of creating the hash table in memory…
- Query execution
- How to read an execution plan
- What not to do with SQL Server
- Why cursors are bad
- Why scalar UDFs are expensive
- Datatypes and design
- What is a columnstore index?
- Transaction isolation
Skill Level Intermediate
1. Query Execution
2. What Not to Do with SQL Server
3. Datatypes and Design
4. Temporary Objects
7. Isolation Levels
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