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In the context of relational databases, a column is a set of data values, all of a single type, in a table. Columns define the data in a table, while rows populate data into the table.
Most databases also allow columns to contain complex data like images, whole documents, or even video clips. So, a column allowing data values of a single type does not necessarily mean it only has simple text values like. Some databases go even further and allow the data to be stored as a file on the Operating System, while the column data only contains a pointer or link to the actual file. This is done for the purposes of keeping the overall database size manageable -- a smaller database size means less time taken for backups and less time to search for data within the database
A simple example is a table that stores customer information for a bank. The columns in this table may take the form of: Customer Name; Customer Phone Number; Customer Date of Birth; Customer ID; Postal Code; Address; City; ID Number. A row of data will be each horizontal set that contains data for all the columns listed above, one row for each customer. For example Andrew Jones; 134532452; 12-Jun-1970; 4356; 0100; 12 Maple Drive; New York; 657367.
The term “field” is usually used interchangeably with ”column,” but database purists prefer to use the word “field” to denote a particular value or single item of a column. Thus, a field is the intersection of a row and a column. In the bank example above, a field is formed by the intersection of a row with the column “Customer Name” to form “Andrew Jones”. However, this distinction is ignored by most.