Answer
A hash match creates an in-memory hash table for joins and aggregates.
If memory is insufficient ? spills to TempDB ? huge slowdown.
Quick Answer
Hash Match builds a hash table from the smaller input (build phase), then scans the larger input and probes the hash table (probe phase). Build phase requires memory — if underestimated, it spills to TempDB. Heavy on both memory and TempDB I/O. Common when indexes are missing and inputs are large.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ