For example, Software engineer, Team lead, Project Manager, Project lead, QC engineer, QC Lead, QC manager etc. An employee can belong to one designation at a time.
It means at a time an employee can either be Software engineer or team lead or project manager but not software engineer as well team lead at a same time.
Also the projects can work on different technologies like .Net, SQL Server, Oracle, HTML5 etc. Every project has a start data and end date. A project can work can include many technologies like .net, SQL Server , Java script, HTML5 etc. Most of the time every project work include a front end server technology like JAVA. Asp.net, uses Java script, HTML, CSS as client side technologies and SQL Server, oracle as back end database server. So In this ways a project work can include many technologies as in above example, suppose a project can use Asp.net as server end front end technology, java script, HTML, CSS, AJAX as client side technology and SQL server as back end database server.
What should be the design the database schema (tables, their foreign keys, primary keys etc).