Understanding Clauses vs Statements in MySQL
In MySQL, a **clause** is a component of a SQL statement that performs a specific role, such as filtering, grouping, or ordering data. A **statement**, on the other hand, is a complete SQL command that can be executed by MySQL.
Key Differences Between Clauses and Statements
- A **statement** is a complete command, e.g., `SELECT`, `INSERT`, `UPDATE`, `DELETE`.
- A **clause** is a part of a statement that specifies conditions or operations, e.g., `WHERE`, `GROUP BY`, `HAVING`, `ORDER BY`.
- Statements can execute independently, but clauses cannot—they only make sense within a statement.
- Example: In `SELECT name, salary FROM employees WHERE salary > 50000 ORDER BY name;`, the `SELECT ... FROM ...` is the statement, while `WHERE salary > 50000` and `ORDER BY name` are clauses.
Common MySQL Clauses
- `WHERE` – filters rows based on conditions.
- `GROUP BY` – groups rows for aggregation.
- `HAVING` – filters groups after aggregation.
- `ORDER BY` – sorts the result set.
- `LIMIT` – restricts the number of rows returned.
In essence, clauses are the building blocks of statements. Understanding how to combine them correctly allows you to write precise and efficient SQL queries.