SELECT Lists

Simple Integer Expressions

Simple integer expressions are recomputed row by row.

highlighted = computed this step

Simple integer expressions

This small model supports one integer expression: add two integer columns.

qty plus bonus\text{qty plus bonus}

Read expression rows

The expression is recomputed for 4 source rows.

expression rows=4\text{expression rows}=4

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

Simple integer expressions: base rowsitemqtybonusstatuspen31openmug20opencup21closedtagNULL1open SELECT list itemspositionkindsourceoutput0columnitemitem1addqty plus bonustotal SELECT output rowsitemtotalpen4mug2cup3tagNULL SELECT factsfactvalueinputRowCount4outputRowCount4outputColumnCount2duplicateOutputRows0rowOrdersource_orderdistinctAppliedno

NULL stays NULL

If either side of the addition is NULL, the expression result is NULL.

NULL plus value gives NULL\text{NULL plus value gives NULL}

Summary

Expressions are still exact finite row transforms.

exact expression\text{exact expression}