Comparison Predicates

Base Rows

Each row is checked by one comparison predicate.

highlighted = computed this step

Base rows

A comparison predicate checks one value in each row.

row by row\text{row by row}

Show the rows

The pinned input has 5 rows.

input rows=5\text{input rows}=5

Comparison examples are tiny finite-table transforms with SQL-style TRUE/FALSE/UNKNOWN results; SQL dialect completeness, type coercion, optimizer behavior, indexing, and product claims are out of scope.

Base rows for comparison: base rowsidnameqtycity1alpha3Austin2beta7Boston3gamma7NULL4delta10Denver5epsilonNULLAustin Comparison result per rowsourceleftValueoprightValuetruthoutputRole03eq7FALSEdropped17eq7TRUEkept27eq7TRUEkept310eq7FALSEdropped4NULLeq7UNKNOWNdropped WHERE-style TRUE-only output rowsidnameqtycity2beta7Boston3gamma7NULL Comparison factsfactvalueinputRowCount5trueCount2falseCount2unknownCount1outputRowCount2droppedRowCount3orderedComparisonnowhereKeepsTRUE_only_source_order

One predicate at a time

This book keeps one comparison visible so TRUE, FALSE, and UNKNOWN can be read directly.

one predicate\text{one predicate}

Summary

The output table keeps only rows whose comparison is TRUE.

TRUE rows kept\text{TRUE rows kept}