WHERE vs HAVING

Base Rows

WHERE and HAVING start from the same pinned rows.

highlighted = computed this step

Base rows

WHERE and HAVING both start from the same pinned rows.

same base rows\text{same base rows}

Show the rows

The input has 6 rows before any row or group filter runs.

input rows=6\text{input rows}=6

HAVING examples are tiny finite group-filter transforms; SQL dialect completeness, optimizer behavior, indexing, and product claims are out of scope.

Base rows before filters: base rowsidregionstatusqty1eastopen22eastopen33westopen14westclosed45northNULL26northopen1 WHERE before groupingsourceinputwhereTruthgroupedRole0[1, east, open, 2]TRUEgrouped1[2, east, open, 3]TRUEgrouped2[3, west, open, 1]TRUEgrouped3[4, west, closed, 4]TRUEgrouped4[5, north, NULL, 2]TRUEgrouped5[6, north, open, 1]TRUEgrouped GROUP BY bucketskeysourceRowsrowCount[east][0, 1]2[west][2, 3]2[north][4, 5]2 Aggregate facts per groupkeysourceRowsaggregates[east][0, 1]{n:2, total_qty:5}[west][2, 3]{n:2, total_qty:5}[north][4, 5]{n:2, total_qty:3} HAVING result per groupkeypredicatetruthoutputRole[east]noneTRUEkept[west]noneTRUEkept[north]noneTRUEkept HAVING output groupsregionntotal_qtyeast25west25north23 HAVING factsfactvalueinputRowCount6whereKeptRows6whereDroppedRows0groupCount3aggregateCount2outputGroupCount3havingTrueCount3havingFalseCount0havingUnknownCount0groupOrderfirst_seen_after_wherepipelineWHERE_before_GROUP_BY_then_HAVING

Read the pipeline

The diagram keeps base rows, WHERE, groups, aggregates, HAVING, and output visible.

visible pipeline\text{visible pipeline}

Summary

The rest of the book changes the boundary where filtering happens.

boundary matters\text{boundary matters}