Migrating from a Relational Database to DynamoDB

Files used in the solution videos for this lab can be found here.

We are stepping into the role of a data migration engineer. We've been tasked with migrating a database of employees from MySQL to DynamoDB. We have been provided with several common queries (access patterns) that need to be maintained and optimized through the migrations to DynamoDB. We need to investigate the source database and create a data model that will inform our Database Migration Service mapping rules and DynamoDB table structure. We will then create our DynamoDB table and a DMS task to move data from our source database to our newly created DynamoDB table. The source database has been prepared with a table named dms_source that contains the denormalized data that should be migrated to our DynamoDB table.

Our database was normalized to save space, but we need to move our data in a denormalized way. Fortunately for us, our database already includes denormalized data that was created from the normalized tables in the database. As such, we only need read-only access to our database. The following MySQL command was used to create our dms_source table and is included for your reference:

CREATE TABLE
    dms_source
SELECT
    employees.*,
    titles.title,
    titles.from_date AS title_from_date,
    titles.to_date AS title_to_date,
    salaries.salary,
    salaries.from_date AS salary_from_date,
    salaries.to_date AS salary_to_date,
    dept_emp.dept_no as department_number,
    departments.dept_name as department_name,
    dept_emp.from_date AS dept_from_date,
    dept_emp.to_date AS dept_to_date
FROM (SELECT * FROM employees LIMIT 500) employees
    INNER JOIN titles ON employees.emp_no=titles.emp_no
    INNER JOIN salaries ON employees.emp_no=salaries.emp_no
    INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
    INNER JOIN departments ON dept_emp.dept_no=departments.dept_no;

Frequent Queries (Access Patterns)

DynamoDB will allow us to utilize the query function on our new table, but the following queries are shown as an example of what can be done through the CLI to obtain the requested access patterns. Below is a list of the frequent queries or access patterns requested for this lab:

• Get the department name, title, employee ID, first name, last name, and salary for all employees in the Development department with the title Senior Engineer (only including most recent salary):

  SELECT
  departments.dept_name AS "Department Name",
  titles.title AS "Title",
  employees.emp_no AS "Employee ID",
  employees.first_name AS "First Name",
  employees.last_name AS "Last Name",
  salaries.salary AS "Salary"
  FROM employees
  INNER JOIN salaries ON employees.emp_no=salaries.emp_no
  INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments ON dept_emp.dept_no=departments.dept_no
  INNER JOIN titles on employees.emp_no=titles.emp_no
  WHERE
  salaries.to_date="9999-01-01"
  AND
  departments.dept_name="Development"
  AND
  titles.title="Senior Engineer";

• Get all information about an employee in the Production department with the full name Hercules Benzmuller:

  SELECT
  employees.*,
  titles.title,
  titles.from_date AS "Title from",
  titles.to_date AS "Title to",
  salaries.salary,
  salaries.from_date AS "Salary from",
  salaries.to_date AS "Salary to",
  departments.dept_name,
  dept_emp.from_date AS "Department from",
  dept_emp.to_date AS "Department to"
  FROM employees
  INNER JOIN titles on employees.emp_no=titles.emp_no
  INNER JOIN salaries ON employees.emp_no=salaries.emp_no
  INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments ON dept_emp.dept_no=departments.dept_no
  WHERE
  departments.dept_name="Production"
  AND
  employees.first_name="Hercules"
  AND
  employees.last_name="Benzmuller";

• Get all employees with the title Engineer, returning only most recent salary:

  SELECT
  employees.*,
  titles.title,
  titles.from_date AS "Title from",
  titles.to_date AS "Title to",
  salaries.salary,
  salaries.from_date AS "Salary from",
  salaries.to_date AS "Salary to",
  departments.dept_name,
  dept_emp.from_date AS "Department from",
  dept_emp.to_date AS "Department to"
  FROM employees
  INNER JOIN titles on employees.emp_no=titles.emp_no
  INNER JOIN salaries ON employees.emp_no=salaries.emp_no
  INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments ON dept_emp.dept_no=departments.dept_no
  WHERE
  titles.title="Engineer"
  AND
  salary.to_date="9999-01-01";

• Get all employees in the Production department hired between 1999 and 2001:

  SELECT
  employees.*,
  titles.title,
  titles.from_date AS "Title from",
  titles.to_date AS "Title to",
  salaries.salary,
  salaries.from_date AS "Salary from",
  salaries.to_date AS "Salary to",
  departments.dept_name,
  dept_emp.from_date AS "Department from",
  dept_emp.to_date AS "Department to"
  FROM employees
  INNER JOIN titles on employees.emp_no=titles.emp_no
  INNER JOIN salaries ON employees.emp_no=salaries.emp_no
  INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments ON dept_emp.dept_no=departments.dept_no
  WHERE
  departments.dept_name="Production"
  AND
  UNIX_TIMESTAMP(employees.hire_date) BETWEEN UNIX_TIMESTAMP("1999-01-01") AND UNIX_TIMESTAMP("2001-01-01");

• Get all employees in the Development department who had a title change in the 6 months before January 1, 2001:

  SELECT
  employees.*,
  titles.title,
  titles.from_date AS "Title from",
  titles.to_date AS "Title to",
  salaries.salary,
  salaries.from_date AS "Salary from",
  salaries.to_date AS "Salary to",
  departments.dept_name,
  dept_emp.from_date AS "Department from",
  dept_emp.to_date AS "Department to"
  FROM employees
  INNER JOIN titles on employees.emp_no=titles.emp_no
  INNER JOIN salaries ON employees.emp_no=salaries.emp_no
  INNER JOIN dept_emp ON employees.emp_no=dept_emp.emp_no
  INNER JOIN departments ON dept_emp.dept_no=departments.dept_no
  WHERE
  departments.dept_name="Development"
  AND
  UNIX_TIMESTAMP(titles.from_date) BETWEEN UNIX_TIMESTAMP("2000-06-01") AND UNIX_TIMESTAMP("2001-01-01");