Database Management Systems, DBMSs, are used to control, maintain, and use a relational database where the data is stored. A relational database consists of the data records, files, and database objects. An important part of each organization is allowing users to gain access to the data for them to view and manipulated if required. In order for users to do this query languages are used which enable users to write queries and send them to the database to retrieve the appropriate data and return it to them. Queries can also be written to manipulate the data by updating, deleting or inserting it to the database. The Structured Query Language, known as SQL or SEQUEL, is the main query language used by most DBMSs, this is based on relational algebra and relational calculus which was developed by Dr. Edgar Codd for his theory for the relational database. This course discusses the relational algebra operations and relational calculus for a relational database, how to use SQL to manage data in a relational database, and how transactions and concurrency control are used to ensure data integrity and data consistency. It also discusses how security is implemented in a relational database to keep the data secure.