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Phase 4 · SQL & Databases

Topics

Joins & Aggregations

Part of the Data Science Roadmap.

Summary

Combining rows across tables (INNER, LEFT, RIGHT, FULL) and summarizing them with GROUP BY and aggregate functions — how you build a single clean training dataset out of multiple normalized tables.

How to Learn This

  • 1Practice a LEFT JOIN to find rows in one table with no match in another.
  • 2Write a query grouping and aggregating data across a joined multi-table dataset.
  • 3Learn why WHERE can't filter on an aggregated value, but HAVING can.

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SQL Fundamentals

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Window Functions

More topics in SQL & Databases

SQL FundamentalsWindow FunctionsQuery OptimizationNoSQL Basics (MongoDB Overview)Data Warehouses (BigQuery, Snowflake)
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