Draw an E-R diagram its related tables showing its integrity constraints.
To draw an Entity-Relationship (E-R) diagram with related tables and integrity constraints, you can follow these steps:
1. Identify entities: Start by identifying the main entities in your system or database. These entities represent real-world objects or concepts. For example, if you are designing a database for a library system, entities might include books, authors, and borrowers.
2. Determine relationships: Next, determine the relationships between the entities. Relationships describe how entities are connected or associated with each other. For instance, in our library example, a relationship might exist between books and authors, representing the fact that an author can write multiple books.
3. Define attributes: For each entity, identify the relevant attributes or properties. These attributes describe the characteristics of the entities. Continuing with the library example, attributes for the books entity might include title, ISBN, and genre.
4. Create the E-R diagram: Now, you can start creating the E-R diagram. Use rectangles to represent entities, diamonds to represent relationships, and ovals to represent attributes. Place the entities on the diagram and connect them with lines to represent relationships.
5. Add cardinality and participation constraints: Determine the cardinality and participation constraints for each relationship. Cardinality defines the number of instances of one entity that can be associated with another entity. Participation constraints specify whether participation in a relationship is mandatory or optional. Add these constraints to the relationship lines in the diagram.
6. Convert to tables: Based on the E-R diagram, convert the entities and relationships into tables. Each entity becomes a table, and the attributes become columns within that table. The relationships between entities are represented using foreign key columns.
7. Apply integrity constraints: Finally, apply integrity constraints to the tables. Integrity constraints ensure the accuracy and consistency of data within the database. Common constraints include primary key constraints, foreign key constraints, unique constraints, and not null constraints. These constraints can be specified during table creation or later on using SQL statements.
It's important to note that the level of detail in an E-R diagram and corresponding tables with integrity constraints will depend on the complexity of your system or database. So, make sure to analyze your specific requirements and adjust the steps accordingly.