UPDATE Statements

Honest by Construction

Expected UPDATE facts are assertions only.

highlighted = computed this step

Honest by construction

Expected UPDATE facts are assertions only.

compiler is source of truth\text{compiler is source of truth}

Render checked facts

The guarded UPDATE matches 1 row and changes 1 cell.

matched=1\text{matched}=1

UPDATE examples are tiny finite row modifications; SQL dialect completeness, joins in UPDATE, subqueries, triggers, constraints, transactions, locks, indexes, optimizer behavior, performance, and product behavior are out of scope.

Honest by construction: base rowsidownerstatuspointsnote1Adaopen10seed2Benopen20call3Cydone15NULL4DeeNULL5draft WHERE chooses rowssourcevaluecompareTotruthkeptForUpdate012FALSEno122TRUEyes232FALSEno342FALSEno SET assignmentscolumnnewValuepoints25 Row-by-row updatesourcematchedassignmentsafter0no()(1, Ada, open, 10, seed)1yes({column:points, old:20, new:25})(2, Ben, open, 25, call)2no()(3, Cy, done, 15, NULL)3no()(4, Dee, NULL, 5, draft) Rows after UPDATEidownerstatuspointsnote1Adaopen10seed2Benopen25call3Cydone15NULL4DeeNULL5draft UPDATE factsfactvaluebaseRowCount4finalRowCount4matchedRowCount1setColumnCount1changedCellCount1nullAssignmentCount0updateStatusappliedwhereUnknownCount0

Try to tamper

Wrong expected facts, derived sidecars, unsupported WHERE kinds, missing columns, bools, and floats fail closed.

tamper rejected\text{tamper rejected}

Summary

This book shows exact finite UPDATE behavior only.

scoped UPDATE model\text{scoped UPDATE model}