1. Data Integrity
1.1 Database Integrity
It is used to ensure that the data stored in the database is valid, that is, the validity and accuracy of the data.
Ensuring Data Integrity = Add constraints to tables when they are created.
Classification of completeness:
- entity integrity (row integrity);
- domain integrity ( column integrity);
- Referential integrity (relational table integrity):
Primary key constraint: primary key
Unique constraint: unique [key]
Not-null constraint: not null
Default constraints: default
Automatic growth: auto_increment
Foreign key constraint : foreign key
Recommendation: These constraints should be set when creating the table
Note: Use spaces between multiple constraints
1.2 Entity Integrity
Entity: that is, a row (a record) in the table represents an entity (entity)
The role of entity integrity: to identify that each row of data is not repeated
Constraint types: primary key constraints, unique constraints, auto-growth columns
1.2.1 Primary key constraint (primary key)
Not perfect, to be updated!