OraclePLSQL-Page5

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👉Data Constraints

Business rules, which are enforced on data being stored in a table are called constraints.

Types of data constraints:

1)I/O Constraint

2)Business Rule Constraint


👉I/O Constraint

This data constraint determines the speed at which data can be inserted or extracted from a table. 

Types of I/O Constraint

✅Primary Key

✅Foreign Key

✅Unique Key


👉Primary Key

Primary Key is a column or a set of columns that uniquely identifies a row. Its main purpose is the record uniqueness.

Primary Key will not allow duplicate values.

Primary Key will also not allow null values.

One table can combine up to 16 columns in a composite primary key.


👉Primary Key Constraint defined at Column Level:

👉Primary Key Constraint defined at Table Level:

👉Simple Primary Key

A single-column primary key is called a simple primary key.


👉Composite Primary Key

A multicolumn primary key is called composite primary key.

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