Suppose you have a table R with scheme S which is in 1NF but not in 2NF. Here’s the general algorithm for normalizing a table from 1NF to 2NF. DELETE: If we remove the Algorithms course, we also remove the lecturer James Cormen.UPDATE: You can change the lecturer for the course Relational Databases by changing just one row in Courses2.Simply add the course to Courses2 without adding rows to CourseTextbooks. INSERT: You can now add a course with no textbooks.The following problems have been removed in the new database: The candidate key in this table is the set, and there are no functional dependencies on only a part of a key, so it is in 2NF. lecturer -> department: The lecturer determines the department.course -> lecturer, department: The course determines the lecturer and the department.course, textbook -> lecturer, department: The course and textbook determine the lecturer and the department.There are three non-trivial functional dependencies in this table: These problems come from the fact that this table is not in 2NF. DELETE: If you remove the Algorithms course, you also remove the lecturer James Cormen.UPDATE: To change the lecturer for the course Relational Databases, you have to change two rows.INSERT: You can't add a course with no textbooks.There are several problems with various operations on data in this table: The table is in the first normal form, since all column values are atomic. We’ll work with a table named Courses1, which contains information about courses offered at a certain university: the titles of the courses, the lecturers, the departments, and the recommended textbooks for each course. We’ll also discuss problems with 1NF tables that are solved when you normalize them into 2NF. In this article, we’ll show you an example of normalization from 1NF through 2NF into 3NF. Typically, you normalize a table from 1NF to 3NF in two steps: first you normalize it into 2NF, then you normalize that into 3NF. All non-prime attributes are directly (non-transitively) dependent on the entire candidate key.You should also know how to normalize a table that’s not in 3NF into one in 3NF. If you want to be a database designer, you should know how to check if a table is in 3NF. In practice, the most important normal form is the third normal form (3NF). Every database designer should know the rules for different normal forms. We present a practical example of how to normalize a table that is in the first normal form (1NF) into a set of tables in the third normal form (3NF).ĭatabase normalization is a very important concept in database design.
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