01 Theory
Parts of Table¶
Rows - Records/Tuples
Columns - Fields/Attributes
Drawbacks of File System (Spreadheets)¶
- Data redundancy and inconsistency
- duplication of information in different files
- different file formats
- Difficulty in accessing data
- Data isolation
- multiple files (scattered all over the place)
- Integrity problems Data validation and constraints is difficult
- Collaboration is difficult
- Uncontrolled Access
- Security Problems
Abstraction¶
Data hiding
| Level of Abstraction | |
|---|---|
| Physical Level | describes how record is stored |
| Logical Level | describes what data is stored, and the relationship between data |
| View Level | describes information hiding |
View of data¶
IDK¶
Schema is the skeleton of the table (without data)
Instances is the content of the table (similar to tuples)
Entity-Relationship Model¶
Entity is a table
Relation is the primary key??