SELECT Lists

Aliases Rename Output Labels

Aliases rename output labels.

highlighted = computed this step

Aliases rename output labels

An alias changes the output label without changing the source value.

alias labels\text{alias labels}

Read renamed labels

The output labels are label and count.

labels renamed\text{labels renamed}

SELECT-list examples are tiny finite-table transforms; DISTINCT, aggregation, type coercion, optimizer behavior, and database-product claims are out of scope.

Aliases rename output labels: base rowsitemqtybonusstatuspen31openmug20opencup21closedtagNULL1open SELECT list itemspositionkindsourceoutput0columnitemlabel1columnqtycount SELECT output rowslabelcountpen3mug2cup2tagNULL SELECT factsfactvalueinputRowCount4outputRowCount4outputColumnCount2duplicateOutputRows0rowOrdersource_orderdistinctAppliedno

Values still come from source columns

The values under label come from item, and the values under count come from qty.

same values, new labels\text{same values, new labels}

Summary

Aliases are labels, not a new computation by themselves.

label only\text{label only}