joins
Applied AI interview questions tagged joins, across every topic.
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Concepts behind "joins"
The curriculum that explains the ideas these questions test.
Foundational
SQL JoinsJoins combine rows across tables on a matching condition, and the join type (inner, left, right, full, semi, anti) controls which non-matching rows survive. Applied AI interviews probe joins because they are the single most error-prone SQL construct: the wrong type silently drops or duplicates rows, and a non-unique join key fans out your row count without raising an error.🗄️ Data & SQL Engineering
Core
Query Execution and OptimizationA query optimizer turns your SQL into a physical plan: which tables to scan, in what join order, and whether to use a hash join, sort, or index lookup. Reading an EXPLAIN plan tells you why a query is slow (a full scan on a huge table, a bad join order that explodes intermediate rows, a sort that spilled to disk) and which lever fixes it. Applied-AI interviews probe this because the difference between a 30-second and a 0.3-second query is usually understanding the plan, not rewriting the logic.🗄️ Data & SQL EngineeringSign in