SQL Reference

SQL statements, clauses, operators and functions. Examples run on the practice shop database.

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Keyword	Type	Description
SELECT	Statement	Chooses columns to return.
SELECT DISTINCT	Statement	Returns only different values.
FROM	Clause	Names the table to read.
WHERE	Clause	Filters rows.
ORDER BY	Clause	Sorts the result.
LIMIT	Clause	Limits the number of rows.
OFFSET	Clause	Skips rows before returning.
GROUP BY	Clause	Groups rows for aggregates.
HAVING	Clause	Filters groups.
AS	Clause	Gives a column or table an alias.
AND	Operator	Both conditions must be true.
OR	Operator	Either condition may be true.
NOT	Operator	Reverses a condition.
IN	Operator	Matches any value in a list.
BETWEEN	Operator	Matches a range, inclusive.
LIKE	Operator	Matches a text pattern.
IS NULL	Operator	Tests for no value.
COUNT()	Function	Counts rows.
SUM()	Function	Adds up numbers.
AVG()	Function	The average.
MIN()	Function	The smallest value.
MAX()	Function	The largest value.
ROUND()	Function	Rounds a number.
UPPER()	Function	Upper-case text.
LOWER()	Function	Lower-case text.
LENGTH()	Function	The number of characters.
SUBSTR()	Function	Part of a string.
REPLACE()	Function	Replaces text.
COALESCE()	Function	The first value that is not NULL.
CASE	Function	If-then logic inside a query.
CAST()	Function	Converts a value to another type.
INNER JOIN	Join	Rows with a match in both tables.
LEFT JOIN	Join	All rows from the left table, matched where possible.
CROSS JOIN	Join	Every combination of rows.
UNION	Set	Combines results, removing duplicates.
UNION ALL	Set	Combines results, keeping duplicates.
EXISTS	Subquery	True if a subquery returns rows.
Subquery	Subquery	A query inside another query.
INSERT INTO	Statement	Adds rows.
UPDATE	Statement	Changes rows.
DELETE	Statement	Removes rows.
CREATE TABLE	Statement	Creates a table.
ALTER TABLE	Statement	Changes a table.
DROP TABLE	Statement	Deletes a table.
CREATE INDEX	Statement	Speeds up lookups on a column.
PRIMARY KEY	Constraint	Uniquely identifies each row.
NOT NULL	Constraint	The column must have a value.
DEFAULT	Constraint	A value used when none is given.
UNIQUE	Constraint	No two rows may share the value.