COALESCE

Literal Default Fallback

A literal can be a visible fallback value.

highlighted = computed this step

Literal default fallback

A literal can be the last fallback value.

literal fallback\text{literal fallback}

Read literal-default rows

The literal default is used for 2 rows.

literal rows=2\text{literal rows}=2

COALESCE examples are tiny finite row transforms with SQL-style NULL choice behavior; SQL dialect completeness, type coercion, optimizer behavior, indexing, and product claims are out of scope.

Literal default fallback: base rowsnameemailbackupnicknameAdaada@exampleada@backupNULLBeaNULLbea@backupBCalNULLNULLCalDeeNULLNULLNULL COALESCE argument choicesourcearg valueschosenIndexresultresultSource0[ada@example, ada@backup, missing]0ada@exampleemail1[NULL, bea@backup, missing]1bea@backupbackup2[NULL, NULL, missing]2missingliteral3[NULL, NULL, missing]2missingliteral COALESCE output rowsnameemailbackupnicknamecontactAdaada@exampleada@backupNULLada@exampleBeaNULLbea@backupBbea@backupCalNULLNULLCalmissingDeeNULLNULLNULLmissing COALESCE factsfactvalueinputRowCount4argCount3outputRowCount4firstArgRows1fallbackRows3literalDefaultRows2allNullRows0rowOrdersource_orderwhereContrastvalue_choice_not_truth_filter

No hidden value

The default appears because it is an authored argument, not because the compiler invents it.

authored default only\text{authored default only}

Summary

A literal default is a visible final argument.

visible default\text{visible default}