Description
A relational database management system must show its data as two-dimensional tables, of columns and rows, but store it as one-dimensional strings. For example, a database might have this table.
| EmpId | Lastname | Firstname | Salary |
|---|---|---|---|
| 1 | Smith | Joe | 40000 |
| 2 | Jones | Mary | 50000 |
| 3 | Johnson | Cathy | 44000 |
This simple table includes an employee identifier (EmpId), name fields (Lastname and Firstname) and a salary (Salary).
This table exists in the computer's memory (RAM) and storage (hard drive). Although RAM and hard drives differ mechanically, the computer's operating system abstracts them. Still, the database must coax its two-dimensional table into a one-dimensional series of bytes for the operating system to write to either the RAM, hard drive or both.
A row-oriented database serializes all of the values in a row together, then the values in the next row, and so on.
1,Smith,Joe,40000; 2,Jones,Mary,50000; 3,Johnson,Cathy,44000;A column-oriented database serializes all of the values of a column together, then the values of the next column, and so on.
1,2,3; Smith,Jones,Johnson; Joe,Mary,Cathy; 40000,50000,44000;This is a simplification. Moreover, partitioning, indexing, caching, views, OLAP cubes, and transactional systems such as write ahead logging or multiversion concurrency control all dramatically affect the physical organization. That said, online transaction processing (OLTP)-focused RDBMS systems are more row-oriented, while online analytical processing (OLAP)-focused systems are a balance of row-oriented and column-oriented.
Read more about this topic: Column-oriented DBMS
Famous quotes containing the word description:
“Once a child has demonstrated his capacity for independent functioning in any area, his lapses into dependent behavior, even though temporary, make the mother feel that she is being taken advantage of....What only yesterday was a description of the child’s stage in life has become an indictment, a judgment.”
—Elaine Heffner (20th century)
“To give an accurate description of what has never occurred is not merely the proper occupation of the historian, but the inalienable privilege of any man of parts and culture.”
—Oscar Wilde (1854–1900)
“A sound mind in a sound body, is a short, but full description of a happy state in this World: he that has these two, has little more to wish for; and he that wants either of them, will be little the better for anything else.”
—John Locke (1632–1704)