SQL Keywords Reference

A quick reference guide for essential SQL Reserved Keywords, categorized by functional language subset.

1. Data Query Language (DQL)

Used to fetch data from database tables.

Keyword	Description
`SELECT`	Specifies columns to retrieve from a table.
`FROM`	Specifies the source table or view.
`WHERE`	Filters records based on search conditions.
`GROUP BY`	Groups rows with identical data into summary rows.
`HAVING`	Filters groups created by `GROUP BY`.
`ORDER BY`	Sorts the result set ascending (`ASC`) or descending (`DESC`).
`DISTINCT`	Removes duplicate rows from the query output.
`LIMIT` / `TOP`	Constrains the maximum number of rows returned.

Used to add, modify, or remove data rows.

Keyword	Description
`INSERT INTO`	Adds new rows of data into a table.
`UPDATE`	Modifies existing values inside a table.
`DELETE`	Removes specific rows from a table based on conditions.
`MERGE` / `UPSERT`	Performs `INSERT`, `UPDATE`, or `DELETE` in a single atomic operation.

Used to define, alter, and manage database schema structures.

Keyword	Description
`CREATE`	Creates database objects (tables, views, indexes, procedures).
`ALTER`	Modifies the structure of an existing database object.
`DROP`	Deletes a database object along with all its data and structure.
`TRUNCATE`	Efficiently removes all rows from a table without logging individual row deletes.

Used to combine rows from two or more tables based on related columns.

Keyword	Description
`JOIN` / `INNER JOIN`	Returns matching rows present in both tables.
`LEFT JOIN`	Returns all records from the left table, and matched records from the right table.
`RIGHT JOIN`	Returns all records from the right table, and matched records from the left table.
`FULL JOIN`	Returns records when there is a match in either left or right table.
`CROSS JOIN`	Produces the Cartesian product of rows from both tables.
`ON`	Specifies the condition for joining two tables.
`USING`	Concise shorthand join condition when columns in both tables share the exact same name.

Used within conditional filtering statements (WHERE, HAVING).

Keyword	Description
`AND`	Combines multiple conditions; evaluates to true if all conditions are true.
`OR`	Combines multiple conditions; evaluates to true if any condition is true.
`NOT`	Inverts the truth value of a condition.
`IN`	Checks if a value matches any value within a defined list or subquery.
`BETWEEN`	Checks if a value falls inclusively within a specified range.
`LIKE` / `ILIKE`	Matches string patterns using wildcards (`%` for strings, `_` for single characters).
`IS NULL` / `IS NOT NULL`	Evaluates whether a value is empty/absent.
`EXISTS`	Tests whether a subquery returns at least one row.

Used to enforce data integrity during table definition.

Keyword	Description
`PRIMARY KEY`	Uniquely identifies each row in a table (implies `NOT NULL` + `UNIQUE`).
`FOREIGN KEY`	Enforces a link between columns in two tables (referential integrity).
`REFERENCES`	Identifies the parent table and column target for a `FOREIGN KEY`.
`UNIQUE`	Ensures all values stored within a column are distinct.
`NOT NULL`	Prevents empty/null values from being inserted into a column.
`CHECK`	Validates that column values satisfy a custom expression condition.
`DEFAULT`	Defines a default value when no explicit value is provided during insertion.

Used for conditional logic branching and set operations.

Keyword	Description
`CASE` / `WHEN` / `THEN` / `ELSE`	Implements standard IF-THEN-ELSE conditional evaluation logic within queries.
`COALESCE`	Evaluates arguments in order and returns the first non-null value.
`UNION`	Combines results from multiple queries into a single dataset, removing duplicates.
`UNION ALL`	Combines results from multiple queries into a single dataset, keeping duplicates.
`INTERSECT`	Returns only rows that are output by both queries.
`EXCEPT` / `MINUS`	Returns rows from the first query that do not exist in the second query.
`WITH`	Defines a Common Table Expression (CTE) or temporary named result set.

Used for administrative security and transaction safety.

Keyword	Description
`GRANT`	Gives user accounts privileges to access or modify database objects.
`REVOKE`	Removes previously assigned access privileges from users or roles.
`COMMIT`	Permanently saves all modified transaction operations to disk.
`ROLLBACK`	Cancels all pending changes in the current transaction, restoring prior state.
`SAVEPOINT`	Sets an intermediate undo checkpoint within a multi-step transaction block.