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Data Integrity and ER Diagrams
Agenda
- Data Integrity
- ER Diagrams
- Functional Dependencies
- Normalization
Key Terms
Schema
refers to the organization of data as a blueprint of how the database is constructed
In a relational database, the schema defines the tables, fields, relationships, views, indexes, packages, procedures, functions, queues, triggers, types, sequences, materialized views, synonyms, database links, directories, XML schemas, and other elements
Data Integrity
Entity Integrity
Referential integrity
Domain integrity
User-defined integrity
ER Diagrams
Schema
A schema is a blueprint of a database. It is created before you actually construct the database so that the schema design can be reviewed. Schema diagrams are also a great way to document the database structure in one place.
Remember our student's database from the previous lesson? We had the three following tables
students(id, name, age, address, phone, email, batch ID)mentors(id, name, age, address, phone, email)batches(id, name, mentor, start date, type, mentor ID)
So each table has ID as primary key. The students table has a batch ID field that references the batches table and the batches table has a mentor ID field that references the mentors table. These are examples of foreign keys. These are some the items that are present in a schema. A schema will also contain indexes, constraints, and other items that are present in a table.
Following is a schema diagram for the above database. Note that the primary key is not highlighted here, which ideally should be.
Note
Try it yourself.
Go to this website and import this diagram.
Try adding a new column or even a new table.