Normalised entity relationship diagram visio

normalised entity relationship diagram visio

Prepare a FULLY NORMALIZED Entity Relationship diagram in VISIO (where all entities are in 3NF or third normalized form). Please make it pretty intricate and. Answer to Create a Normalized Entity-Relationship Diagram (ERD) to 3NF for the Must use a data modeling tool such as MS Visio or Oracle SQL Developer. To explain the concept of relation database and normalization of data and how it is structured in RDBMS.

Use the Entity Relationship stencil to model databases that are based on the SQL92 and earlier standards. Use the Object Relational stencil, which has additional shapes for working with types, to model databases that are based on SQL99 and later standards. The Database Model diagram is only available in certain versions of Visio.

See Can't find the database modeling features? This article describes how you can create a database model and what you can do with the model after you create it.

Data Modeling: Entity-Relationship Diagram (ER Diagram)

To start your database model diagram, do one of the following: Create a new model diagram from scratch If you don't have an existing database that you want to use as a starting place, you can start with a blank Database Model and add your own tables and relationships.

Click the File tab. On the Database tab, in the Manage group, click Display Options. In the Database Document Options dialog box, select the symbol set that you want to use and other table and relationship options, and then click OK.

Use an existing database as a starting point If you have a database that you want to model so that you can understand it better or use it as a starting place for a new model, you can use the Reverse Engineer Wizard to extract the schema, or structure, of the database and build a new model.

Before you start the wizard: If you are reverse engineering a Microsoft Excel workbook, before you start the wizard you need to open the workbook and name the group or range of cells that contains the column headings. If you want to use more than one worksheet, just name the group of column cells in each worksheet. These ranges are treated like tables in the wizard.

For more information about how to name a range of cells, see the topic in your Excel help titled Define named cell references or ranges. For best results, set your default driver to the target database that you want to reverse engineer before you run the Reverse Engineer Wizard. This step ensures that the wizard maps the native data types correctly and that all the code that is extracted by the wizard is correctly displayed in the Code window.

On the Database tab, in the Model group, click Reverse Engineer. On the first screen of the Reverse Engineer Wizard, do the following: Select the database driver for your database management system DBMS. Select the data source of the database that you are updating. If you have not already created a data source for the existing database, click New to do so now. When you create a new source, its name is added to the Data Sources list.

When you are satisfied with your settings, click Next. Follow the instructions in any driver-specific dialog boxes. For example, in the Connect Data Source dialog box, type the user name and password, and then click OK. If you use the ODBC Generic Driver, you may receive an error message that indicates that the reverse engineered information may be incomplete. Select the check boxes for the type of information that you want to extract, and then click Next.

Some items may be unavailable appear grayed out because not all database management systems support all the kinds of elements that the wizard can extract. Select the check boxes for the tables and views, if any that you want to extract, or click Select All to extract them all, and then click Next.

Normalization ERD Exercise ( Entity Relationship Diagram)

If you are reverse engineering an Excel worksheet and don't see anything in this list, it is likely that you need to name the range of cells that contains the column headings in your worksheet. If you selected the Stored Procedures check box, select the procedures that you want to extract, or click Select All to extract them all, and then click Next. Select whether you want the reverse engineered items to be added automatically to the current page.

You can choose to have the wizard automatically create the drawing, in addition to listing the reverse engineered items in the Tables and Views window. If you decide not to have the drawing created automatically, you can drag the items from the Tables and Views window onto your drawing page to manually assemble the database model. Review your selections to verify that you are extracting the information that you want, and then click Finish. The wizard extracts the selected information and displays notes about the extraction process in the Output window.

This ability is limited to only VisioModeler 2. On the Database tab, in the Model group, click Import, and then click the model type.

Create a Database Model (also known as Entity Relationship diagram) - Visio

Type the path and file name for the model that you want to import, or click the Browse button to locate the model file, and then click Open.

In the Import dialog box, click OK. Visio imports the file and displays its progress in the Output window. The imported tables are displayed in the Tables and Views window. In the Tables and Views window, select the tables that you want to model, and then drag them onto the drawing page.

normalised entity relationship diagram visio

After you create a database model diagram, the work of refining the diagram begins. You can add and customize tables and views, create relationships, and customize columns and data types. Tables Use the Entity shape to create a table in your diagram.

From either the Entity Relationship or Object Relational stencil, drag an Entity shape onto the drawing. Double-click the shape to open the Database Properties window.

Under Categories, click Definition and type a name for the table. Under Categories, click Columns, type a name, and choose a data type.

normalised entity relationship diagram visio

Select the Req'd check box for columns that can't have null values. Select the PK primary key check box for columns that uniquely identify each row in the database table.

Columns Use the Database Properties window to add or change properties for columns, including data types and primary keys. Double-click the table in your diagram. In the Database Properties window, under Categories, click Columns. Click in the first empty Physical Name cell, and type a name. To change the data type for a column, click the column's Data Type field, and then select a data type from the list or type it into the list. For example, you can type decimal 8,2 or char To prevent null values, select the Req'd check box.

normalised entity relationship diagram visio

In other words, the Fee attribute values are not specific to the SID value of a student, but rather the BuildingName value. The entity instance of transitive dependency is shown in Figure 5. Figure 5 Multi-valued dependency equivalency in ERD occurs when attributes within an entity instance have more than one value. This is a situation when some attributes within an entity instance have maximum cardinality of N more than 1. When an attribute has multiple values in an entity instance, it can be setup either as a composite key identifier of the entity type, or split into a weak entity type.

For example, consider the following entity type Student Details as shown in Figure 6. The composition of entity identifier is due to the fact that a student has multiple MajorMinor values along with being involved in multiple activities. The multi-valued dependency affects the key structure. This means that a SID value is associated with multiple values of MajorMinor and Activity attributes, and together they determine other attributes. The entity instance of Student Details entity type is shown Figure 7.

Each normal form rule and its application is outlined. First Normal Form 1NF The first normal form rule is that there should be no nesting or repeating groups in a table. Now an entity type that contains only one value for an attribute in an entity instance ensures the application of first normal form for the entity type.

So in a way any entity type with an entity identifier is by default in first normal form. For example, the entity type Student in Figure 2 is in first normal form.

Second Normal Form 2NF The second normal form rule is that the key attributes determine all non-key attributes. A violation of second normal form occurs when there is a composite key, and part of the key determines some non-key attributes. The second normal form deals with the situation when the entity identifier contains two or more attributes, and the non-key attribute depends on part of the entity identifier. For example, consider the modified entity type Student as shown in Figure 8. The entity type has a composite entity identifier of SID and City attributes.

Figure 8 An entity instance of this entity type is shown in Figure 9. Now, if there is a functional dependency City? Status, then the entity type structure will violate the second normal form.

Figure 9 To resolve the violation of the second normal form a separate entity type City with one-to-many relationship is created as shown in Figure The relationship cardinalities can be further modified to reflect organizational working. In general, the second normal form violation can be avoided by ensuring that there is only one attribute as an entity identifier.

This normal form is violated when there exists a dependency among non-key attributes in the form of a transitive dependency. For example consider the entity type Student as shown in Figure 4. In this entity type, there is a functional dependency BuildingName? Fee that violates the third normal form. Transitive dependency is resolved by moving the dependency attributes to a new entity type with one-to-many relationship.

In the new entity type the determinant of the dependency becomes the entity identifier. The resolution of the third normal form is shown in Figure The Boyce-Codd normal form rule is that every determinant is a candidate key. Even though Boyce-Codd normal form and third normal form generally produce the same result, Boyce-Codd normal form is a stronger definition than third normal form.

Every table in Boyce-Codd normal form is by definition in third normal form. Boyce-Codd normal form considers two special cases not covered by third normal form: Part of a composite entity identifier determines part of its attribute, and a non entity identifier attribute determines part of an entity identifier attribute.

These situations are only possible if there is a composite entity identifier, and dependencies exist from a non-entity identifier attribute to part of the entity identifier. For example, consider the entity type StudentConcentration as shown in Figure The entity type is in third normal form, but since there is a dependency FacultyName?

MajorMinor, it is not in Boyce-Codd normal form. Figure 12 To ensure that StudentConcentration entity type stays in Boyce-Codd normal form, another entity type Faculty with one-to-many relationship is constructed as shown in Figure Figure 13 Fourth Normal Form 4NF Fourth normal form rule is that there should not be more than one multi-valued dependency in a table. For example, consider the Student Details entity type shown in Figure 6.

Now, during requirements analysis if it is found that the MajorMinor values of a student are independent of the Activity performed by the student, then the entity type structure will violate the fourth normal form.

normalised entity relationship diagram visio

To resolve the violation of the fourth normal form separate weak entity types with identifying relationships are created as shown in Figure The StudentFocus and StudentActivity entity types are weak entity types. It is now presumed that the Student entity type has the functional dependency SID? Due to the similarity in the notion of an entity type and a relation, normalization concepts when explained or applied to an ERD may generate a richer model.

Normalizing with Entity Relationship Diagramming | az-links.info

Also, such an application enables a better representation of user working requirements. This application now results in the specification of additional guidelines for refining an ERD. These guidelines can be stated as follows: There should be only one dependency in each entity type where the determinant is the entity identifier. There should not be any additional dependency among the non entity identifier attributes.

Any such additional dependency should be represented by a new entity type with one-to-many relationship. If there is a composite entity identifier of three or more attributes it should be ensured that there is only one multi-valued dependency among them.

Study of dependencies among attributes during requirement analysis assist in entity type identifications and cardinality specifications.

Since an ERD represents a relational model schema, a normalization ERD improves the modeling effort thereby facilitating a better fit with organizational working. Enhancing the ER model with integrity methods. Journal of Database Management, 10 4Accuracy in modeling with extended entity relationship and object oriented data models.

normalised entity relationship diagram visio

Journal of Database Management, 4 4 ,