SQL (Structured Query Language) is used to communicate with a database. SQL statements are used to perform tasks such as update data on a database, or retrieve data from a database. Standard SQL commands such as “Select”, “Insert”, “Update”, “Delete”, “Create”, and “Drop” can be used to accomplish almost everything that one needs to do with a database. SQL Select command retrieves data from a database and is returned in a table-like structure called a result-set. Select is the most frequently used action on a database. Insert command is used to add new data to a database and can be combined with a “SELECT” to insert records. Update command updates data values in a database and can update one or more records in a table. Delete permanently removes records from a table. Create is used to generate a database or new table. Drop command is used to remove or delete Indexes, tables, and databases.
Sometimes the simplest precautions can help prevent security breaches. Securing each computer can greatly help protect a company. Implementing password protection and requiring re-logon after a period of inactivity can help protect each user. Training employees to never leave laptops or PDAs unattended is another way to make sure information stays secure. Keeping Security Software Up-To-Date is a must with today’s changing malware and viruses. The use of firewalls, anti-virus and spyware software can help protect from hackers attempting to gain information. Probably one of the easiest and cheapest form of security is the user ability. It is essential to train employees and establishing a written policy about privacy and data security and communicate it to all employees. Educating them about what information is sensitive and what their responsibilities are to protect that data, can help keep a company from any data security breaches.
The three different types of relationships that deal with cardinality are one-to-one, one-to-many, and many-to-many. In a one-to-one relationship, each row in one database table is linked to one and only one other row in another table. An easy to understand example is that one person can only have one driver’s license, and that a driver’s license can only belong to one person. When talking about one-to-many it is typically refereeing the user can have one or more addresses, such as a mailing address and a billing address. The basic concept is that the user can have many different addresses but that address can only belong to one user. A simple example of that is like an employer and its many different employees, but that employee only has one employer. The last of the three is the many-to-many database relationship. It is used where the rows in the first table can map to multiple rows in the second table, and those rows in the second table can also map to different rows in the first table.