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Basic Query Examples
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This notebook demonstrates how to run queries on SingleStore through a series of examples. For simplicity, the sample data in these examples is limited to 10 rows or less per table, which is much smaller than typical workloads. The examples cover various database operations, including index scans, full-table scans, joins, and aggregations.
1. Create a Workspace
To create a workspace, refer to the Creating and Using Workspaces.
2. Create the Database
Select the workspace in your notebook, and create a database.
In [1]:
1%%sql2CREATE DATABASE memsql_example;3USE memsql_example;
3. Create the tables
Create the tables named departments, employees, and salaries.
In [2]:
1%%sql2CREATE TABLE departments /* Creating table for sample data. */(3 id int,4 name varchar(255),5 PRIMARY KEY (id)6);7 8CREATE TABLE employees /* Creating table for sample data. */(9 id int,10 deptId int,11 managerId int,12 name varchar(255),13 hireDate date,14 state char(2),15 PRIMARY KEY (id)16);17 18CREATE TABLE salaries /* Creating table for sample data. */(19 employeeId int,20 salary int,21 PRIMARY KEY (employeeId)22);
4. Populate the tables
Insert the data into the tables.
In [3]:
1%%sql2INSERT INTO departments (id, name) VALUES3 (1, 'Marketing'), (2, 'Finance'), (3, 'Sales'), (4, 'Customer Service');4 5INSERT INTO employees (id, deptId, managerId, name, hireDate, state) VALUES6 (1, 2, NULL, "Karly Steele", "2011-08-25", "NY"),7 (2, 1, 1, "Rhona Nichols", "2008-09-11", "TX"),8 (3, 4, 2, "Hedda Kent", "2005-10-27", "TX"),9 (4, 2, 1, "Orli Strong", "2001-07-01", "NY"),10 (5, 1, 1, "Leonard Haynes", "2011-05-30", "MS"),11 (6, 1, 5, "Colette Payne", "2002-10-22", "MS"),12 (7, 3, 4, "Cooper Hatfield", "2010-08-19", "NY"),13 (8, 2, 4, "Timothy Battle", "2001-01-21", "NY"),14 (9, 3, 1, "Doris Munoz", "2008-10-22", "NY"),15 (10, 4, 2, "Alea Wiggins", "2007-08-21", "TX");16 17INSERT INTO salaries (employeeId, salary) VALUES18 (1, 885219), (2, 451519), (3, 288905), (4, 904312), (5, 919124),19 (6, 101538), (7, 355077), (8, 900436), (9, 41557), (10, 556263);
5. Let's Query!
The SELECT statement
Ask how many rows are in the employees table.
In [4]:
1%%sql2SELECT COUNT(*) from employees;
The ORDER BY clause
List the ID and the name of each employee.
In [5]:
1%%sql2SELECT id, name FROM employees ORDER BY id;
The WHERE clause
List the employees that work in Texas.
In [6]:
1%%sql2SELECT id, name FROM employees WHERE state = 'TX' ORDER BY id;
You can use the same above query by replacing state = 'NY' to list the employees that work in New York.
In [7]:
1%%sql2SELECT id, name FROM employees WHERE state = 'NY' ORDER BY id;
List the employees hired before 2002.
In [8]:
1%%sql2SELECT id, name, hireDate3 FROM employees4 WHERE hireDate < '2002-01-01'5 ORDER BY id;
List employees and their departments.
In [9]:
1%%sql2SELECT e.name, d.name department FROM3 employees e, departments d4 WHERE e.deptId = d.id5 ORDER BY name;
The COUNT function
List the number of employees in each state.
In [10]:
1%%sql2SELECT state, COUNT(*)3 from employees4 group by state5 ORDER BY state;
The MAX function
Highest salary amongst all employees.
In [11]:
1%%sql2SELECT MAX(salary) FROM salaries;
The Subqueries
Employee with the highest salary.
In [12]:
1%%sql2SELECT e.name, s.salary3 FROM employees e, salaries s4 WHERE e.id = s.employeeId and5 s.salary = (SELECT MAX(salary) FROM salaries);
The AVG function
Average salary of employees in each state.
In [13]:
1%%sql2SELECT e.state, AVG(salary)3 FROM employees e4 JOIN salaries s on e.id = s.employeeId5 GROUP BY e.state6 ORDER BY e.state;
The IN operator
List of managers.
In [14]:
1%%sql2SELECT name3 FROM employees4 WHERE id IN (SELECT managerId FROM employees)5 ORDER BY name;
The NOT IN operator
List of non-managers.
In [15]:
1%%sql2SELECT name3 FROM employees4 WHERE id NOT IN (SELECT managerId FROM employees)5 ORDER BY name;
The Joins
Number of employees reporting to each manager.
In [16]:
1%%sql2SELECT m.name, COUNT(*) count3 FROM employees m4 JOIN employees e ON m.id = e.managerId5 GROUP BY m.id6 ORDER BY count DESC;
Number of employees reporting to each employee.
In [17]:
1%%sql2SELECT m.name, COUNT(e.id) count3 FROM employees m4 LEFT JOIN employees e ON m.id = e.managerId5 GROUP BY m.id6 ORDER BY count desc;
Manager of each employee.
In [18]:
1%%sql2SELECT e.name employee_name, m.name manager_name3 FROM employees e4 LEFT JOIN employees m ON e.managerId = m.id5 ORDER BY manager_name;
Total salary of the employees reporting to each manager.
In [19]:
1%%sql2SELECT m.name, sum(salary)3 FROM employees m4 JOIN employees e ON m.id = e.managerId5 JOIN salaries s ON s.employeeId = e.id6 GROUP BY m.id7 ORDER BY SUM(salary) DESC;
Employees in the finance department earning more than their manager.
In [20]:
1%%sql2%%sql3SELECT e.name employee_name, se.salary employee_salary, m.name manager_name, sm.salary manager_salary4FROM employees e5JOIN salaries se ON e.id = se.employeeId6JOIN employees m ON m.id = e.managerId7JOIN salaries sm ON sm.employeeId = m.id8JOIN departments d ON d.id = e.deptId9WHERE d.name = 'Finance'10 AND sm.salary < se.salary11ORDER BY employee_salary, manager_salary;
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About this Template
Examples of basic SQL queries covering various database operations include index scans, full-table scans, joins, and aggregations.
This Notebook can be run in Shared Tier, Standard and Enterprise deployments.
Tags
startersql
License
This Notebook has been released under the Apache 2.0 open source license.
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