Oracle Constraints: Types Explained

Common constraint types in Oracle database include:

1. Primary Key Constraint: Used to uniquely identify each row of data in a table, typically a combination of one or more fields, ensuring uniqueness and non-null values.
2. Foreign Key Constraint is used to ensure the relationship between tables, ensuring that a foreign key value in one table must exist in the primary key column of another table.
3. Unique constraint is used to ensure that the values in specified columns or combination of columns are unique and does not allow duplicates.
4. Not Null Constraint: used to ensure that a specified column does not allow null values.
5. Check Constraint: used to specify that column values must adhere to specific conditions or range, such as limiting the size or format of values.
6. Default Constraint: Used to specify the default value for a column, which will be used if a value is not provided for the column during data insertion.
7. Constraint from a unique index: Using a unique index as a constraint ensures that the values in the column are unique.
8. Check Constraint: A rule that specifies the conditions or range that column values must adhere to, such as limiting the size or format of a value.