SELECT
Chooses the columns returned in the result.
SQL glossary
Concise definitions of concepts used in lessons and exercises.
FROM
Specifies the main table to query.
WHERE
Filters rows before display or aggregation.
JOIN
Connects multiple tables through a shared key.
LEFT JOIN
Keeps every row from the left table, even without a match.
GROUP BY
Groups rows to calculate totals, averages or counts.
HAVING
Filters groups after an aggregation.
ORDER BY
Sorts results in ascending or descending order.
SUM
Adds values from a numeric column.
COUNT
Counts rows.
AVG
Calculates an average.
COALESCE
Replaces NULL with a fallback value.
NULL
Represents a missing value.
Primary key
Unique identifier for a row in a table.
Foreign key
Column used to connect one table to another.