Laws Normalization In Oracle With Examples Pdf


Sunday, May 19, 2019

There are two goals of the normalization process: ▫ eliminate redundant data (for example, storing the same data in more than one table) and. ▫ ensure data. Database Normalization: Explain 1NF, 2NF, 3NF, BCNF With Examples + PDF: The purpose of normalization is to make the life of users easier. Theory of Data Normalization in SQL is still being developed further. For example , there are discussions even on 6th Normal Form. However, in.

Normalization In Oracle With Examples Pdf

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For example, when we try to update one data item having its copies scattered over several places, a few instances get updated properly while a few others are . Normalization is a design technique that is widely used as a guide in designing To understand these anomalies let us take an example of a Student table. Guidelines for ensuring that DBs are normalized → normal forms: 1NF, 2NF, 3NF, BCNF. ↓. Normalization: series of tests on a relation to determine whether it.

It enforces several criteria including: 1 Removing repeating groups in individual tables, 2 Creating separate tables for every set of related data and 3 Identifying related data using the primary key of a given set. Example: Consider a table containing the details of a company.

The fields to be included are employee name, employee ID no, employee location and employee contact no. For better understanding, this will be displayed in a table form.

Some Facts About Database Normalization

Table 1. It brings ambiguity to the database and can generate anomalies.

Hence the need arises to maintain the uniqueness of the field. So the correct first normal form will be obtained upon editing in such a manner.

The correct table will be: Table 1. The extra contact numbers were removed to obtain the required form design. It states that the domain should have values in the relation which are impossible to be broken down into smaller contents of data, with respect to DBMS.

In other words, it maintains two important criteria to be met in order to provide a normalized data with the second normal form tag. To give more clarity to the statements said above, consider a table and two attributes within the table, A and B.

Suppose attribute B is functionally dependent on A, but is not on a proper subset of A.

Normalization of Database

Then B can be considered to be fully functional and dependent on A. A table that is in 1st normal form and contains only a single key as the primary key is automatically in 2nd normal form. Example: Consider a toy shop that has three branches in three different locations.

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A table is prepared indicating the customer IDs, store IDs and store location. Table 2.

Hence the table does not satisfy the second normal form. TABLE 2. By splitting the table, the partial functional dependency is removed and atomicity is achieved for both the tables thus realizing 1NF in the process.

It is also unique across various rows. So, it is also a superkey.

Second normal form (2NF)

A superkey is basically a set of columns such that the value of that set of columns is unique across various rows. That is, no 2 rows have the same set of values for those columns.

Some of the superkeys for the table above are: Course code Course code, professor name Course code, professor mobile number A superkey whose size number of columns is the smallest is called as a candidate key.

For instance, the first superkey above has just 1 column. The second one and the last one have 2 columns. So, the first superkey Course code is a candidate key. A trivial functional dependency means that all columns of B are contained in the columns of A.

Basically, if a set of columns B can be determined knowing some other set of columns A , then A should be a superkey. Superkey basically determines each row uniquely.The table of data is given below. Hence the table does not satisfy the second normal form. Hence, we require both Full Name and Address to identify a record uniquely. Before we proceed let's understand a few things -- What is a KEY?

In other words, it maintains two important criteria to be met in order to provide a normalized data with the second normal form tag.