Glossary · Phase 7 · Software engineering
Subquery
A query inside another query, which runs first and hands its result to the outer one.
Try it now
SQL is written SELECT first but worked out in this order, which is why a WHERE can't use a column alias but ORDER BY can.
Learn it properly
SQL for analysis · Subqueries, CASE, common table expressions, outer joins and window functions on real order data. About 45 minutes.
Other terms from the same lesson
- anti-join: Finding rows with no match in another table, usually a LEFT JOIN followed by WHERE ... IS NULL.
- common table expression: A named step in a SQL query, written with WITH, that later steps can use like a table.
- window function: A SQL calculation across a set of rows, like a rank or a running total, that keeps every row instead of grouping them.
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