Select Basics

Select Distinct Pairs

DISTINCT applies to the whole selected row, not to each column separately.

highlighted = computed this step

Input table

Start with order statuses where one category-status pair repeats.

Order statuses\text{Order statuses}
Order statusesorder_idcategorystatuso1bookpaido2bookpaido3bookrefundedo4penpaid

Select query

Select category and status with DISTINCT across the whole pair.

SELECT DISTINCT category, status\text{SELECT DISTINCT category, status}
SELECT DISTINCT category, statusdistinct category,statusarity 2 rows 3OrderStatusesarity 3 rows 4

Output table

The duplicate book-paid pair collapses, while book-refunded remains a different pair.

distinct row pairs\text{distinct row pairs}
Outputcategorystatusbookpaidbookrefundedpenpaid