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Data and Our Daily Lives
Like it or not, databases have infiltrated our daily lives. Whether you’re creating a document in Microsoft Excel, organizing your email contact list, or programming a web application using SQL, you’re having some form of contact with a database.
While you don’t necessary need to know the definitions of such terms as schema and DBMS for many modern forms of database usage, having a broad understanding of database workings is nice even for the non-programmer.
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Column or Field
Depending on what type of database management system you are working with, the terms column and field are often used interchangeably. Basically, a column represents one attribute of a record in a table. As an example, think about a table containing information from your email contacts list. The entries of your contact list would contain information such as name, email address, and telephone number. Each of these pieces of information would be considered a column or field.
A database is an organized collection of information. This information can be stored as a set of text files or spreadsheets as well as in many other forms. Even a simple hand-written address book that contains basic information such as name, address, and phone number could be considered a database.
Database Management System (DBMS)
A database management system, or DBMS, is a tool or software application used to create and manipulate databases. Common examples of such applications that are used on a wide-scale basis are Google Spreadsheets and Microsoft Excel. Other programs that are more widely used by database developers include MySQL, Microsoft Access, and Microsoft SQL Server.
The datatype of a column is a particular data format allowed in that column. For example, suppose one of the columns of your table is designated to contain the three-letter abbreviation for each month of the year. Then, the datatype of that column would be a character string consisting of exactly three characters.
It’s important that each row of a table contains some column that makes it unique from all the other entries in the table. This column (sometimes it may actually be a group of columns rather than just one) is called the primary key of the table. This column could consist of unique “real" data such as a social security number or customer number, or it may consist of values that are assigned at the time of table creation.
Record or Row
A row or record is an individual entry in a table. In the example mentioned earlier regarding an email contacts list that contained the name, email address, and telephone number of a contact, a row would be represented by one full entry in that list such as: John Smith, email@example.com, 555-555-5555.
The term schema is used in two ways when referring to databases. First off, a table schema describes a particular table in a database with information relating to the various fields and datatypes the table contains. On the other hand, a database schema gives information on the entire database including the relationship between the various tables of the database. This latter type of schema is sometimes referred to as a layout.
SQL, or Structured Query Language, is a programming language used to create and manipulate databases.
A table is one file in a database with a specific, structured type of data. A database can, and usually does, have multiple tables that break down all of the stored information into manageable, related portions.