![]() ![]() Hence we will introduce a new table that stores the salutations Table 1 Employee ID In our example, if there is a name change (male to female), there may be a change in the salutation (Mr., Ms., Mrs., etc.). It should not have any transitive functional dependenciesĪ transitive functional dependency is when a change in a column (which is not a primary key) may cause any of the other columns to change.3NF - Third Normal Formįor a table to be in the third normal form, it should satisfy the following rules: In Table 2, Employee ID is the foreign key. The records can be uniquely identified using this primary key. We have introduced a new column called Employee ID which is the primary key for Table 1. Table 2 contains information on their key skills. Table 1 contains all the employee information. Let’s divide the 1NF table into two tables - Table 1 and Table 2. The primary key should not be functionally dependant on any subset of candidate key.For a table to be in the second normal form, it should satisfy the following rules: In a 2NF table, all the subsets of data that can be placed in multiple rows are placed in separate tables. The table in 1NF will look like this: Salutation Each cell should contain a single value. ![]() For a table to be in the first normal form, it should satisfy the following rules: The most basic form of data normalization is 1NF which ensures there are no two same entries in a group. Assume that a company has a database of all their employees and their key skills as shown in the table below. Let us dive into all these normal forms with the help of an example. The most popular ones are 1NF, 2NF, 3NF, and BCNF. Foreign key - A key that references the primary key of another tableĭata normalization can be divided into different types of normal forms.Composite key - A set of columns used to uniquely identify the rows in a table.Primary key - A single column used to uniquely identify a table.It also helps to identify duplicate information and establish relationships between different tables. A key can be a single column or a combination of columns that uniquely identify the rows (or tuples) in the table. Keys in SQLīefore moving on to the different forms of data normalization, you need to first understand the concept of keys in SQL. Data might become difficult to access as a result of inconsistent dependencies because the path to finding the data may be incomplete or damaged. The wage of the employee must be transferred to the Employees table because it is connected to or dependent upon the employee. Whereas it makes perfect sense for a user to search in the Customers database for a specific customer's address, it might not sound right to do so for the worker who phones on that customer's behalf. If the information is kept solely in the Customers table and not elsewhere in the database, changing a customer's address is significantly simpler to do. If data that already exists in multiple locations needs to be modified, it must be updated in the same manner everywhere. This entails building tables and linking those tables together in accordance with principles intended to safeguard the data and increase the database's adaptability by removing duplication and inconsistent reliance.ĭisk space is wasted by redundant data, and maintenance issues result. ![]() Data organization in a database is done by normalization. ![]()
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