SQL Clauses

Description

SQL clauses are keywords that specify conditions or modify the behavior of SQL statements. They form the building blocks of SQL queries.

Different Clauses

SELECT Clause:

Specifies the columns to be retrieved.

Example:

SELECT name, salary FROM employees;

FROM Clause:

Specifies the table(s) from which to retrieve the data.

Example:

SELECT name, salary FROM employees;

WHERE Clause:

Filters the rows based on a specified condition.

Example:

SELECT name, salary FROM employees WHERE department_id = 10;

GROUP BY Clause:

Groups rows that have the same values in specified columns into aggregated data.

Example:

SELECT department_id, AVG(salary) FROM employees GROUP BY department_id;

HAVING Clause:

Filters groups based on a specified condition (used with GROUP BY).

Example:

SELECT department_id, AVG(salary) FROM employees GROUP BY department_id HAVING AVG(salary) > 50000;

ORDER BY Clause:

Sorts the result set based on one or more columns.

Example:

SELECT name, salary FROM employees ORDER BY salary DESC;

JOIN Clause:

Combines rows from two or more tables based on a related column.

Example:

SELECT employees.name, departments.dept_name
FROM employees
JOIN departments ON employees.dept_id = departments.dept_id;

INSERT INTO Clause:

Adds new rows to a table.

Example:

INSERT INTO employees (name, department_id, salary) VALUES ('John Doe', 10, 60000);

UPDATE Clause:

Modifies existing rows in a table.

Example:

UPDATE employees SET salary = salary + 5000 WHERE department_id = 10;

DELETE Clause:

Removes rows from a table.

Example:

DELETE FROM employees WHERE department_id = 10;

LIMIT/OFFSET Clause:

Specifies the number of rows to return or skip (supported in databases like MySQL, PostgreSQL).

Example:

SELECT * FROM employees LIMIT 10 OFFSET 20;

DISTINCT Clause:

Removes duplicate rows from the result set.

Example:

SELECT DISTINCT department_id FROM employees;