In MariaDB, the SELECT statement is used to retrieve data from one or more tables in the database. It allows you to specify the columns you want to retrieve and filter the rows based on specific conditions. Here's how you can use the SELECT statement in MariaDB with various examples:-
Assuming we have a table named employees with columns employee_id, first_name, last_name, and salary, let's demonstrate various SELECT queries:-
Table: employees
+-------------+-------------+------------+--------+
| employee_id | first_name | last_name | salary |
+-------------+-------------+------------+--------+
| 1 | John | Doe | 50000 |
| 2 | Jane | Smith | 60000 |
| 3 | Michael | Johnson | 55000 |
| 4 | Emily | Brown | 65000 |
+-------------+-------------+------------+--------+
1. Select all columns from the employees table:-
SELECT * FROM employees;
2. Select specific columns (first_name, last_name, salary) from the employees table:-
SELECT first_name, last_name, salary FROM employees;
3. Select employees with a salary greater than 55000:-
SELECT * FROM emplyees WHERE salary > 55000;
4. Select employees with a specific first name (e.g., John):-
SELECT * FROM employees WHERE first_name = 'John';
5. Select employees sorted by salary in descending order:-
SELECT * FROM employees ORDER BY salary DESC;
6. Select the total number of employees:-
SELECT COUNT(*) AS total_employees FROM employees;
7. Select the average salary of employees:-
SELECT AVG(salary) AS average_salary FROM employees;
8. Select distinct last names from the employees table:-
SELECT DISTINCT last_name FROM employees;
These are just a few examples of how to use the SELECT statement in MariaDB. You can modify and expand upon these queries based on your specific requirements and table structure.
Here are five frequently asked questions about the SELECT statement in MariaDB:-
1. What is the SELECT statement used for in MariaDB?
- The SELECT statement is used to retrieve data from one or more tables in a MariaDB database. It allows you to specify which columns you want to retrieve, apply filtering conditions, and order the results as needed.
2. How do I select all columns from a table in MariaDB?
- To select all columns from a table, you can use the asterisk (*) wildcard character. For example: SELECT * FROM table_name; This retrieves all columns and all rows from the specified table.
3. How can I filter the results of a SELECT query in MariaDB?
- You can use the WHERE clause to filter the results based on specific conditions. For example: SELECT * FROM table_name WHERE column_name = 'value'; This will only retrieve rows where the specified column has the specified value.
4. Can I sort the results of a SELECT query in MariaDB?
- Yes, you can use the ORDER BY clause to sort the results based on one or more columns. For example: SELECT * FROM table_name ORDER BY column_name; This will sort the results in ascending order based on the specified column.
5. How can I limit the number of rows returned by a SELECT query in MariaDB?
- You can use the LIMIT clause to specify the maximum number of rows to return. For example: SELECT * FROM table_name LIMIT 10; This will return only the first 10 rows from the specified table.
