what to use in sql to achieve entity integrity

SQL methods to achieve entity integrity are: Primary key constraints: ensure that column values ​​uniquely identify each row. Unique constraints: Ensure that column values ​​are unique in the table. Non-null constraint: prevents column values ​​from being null.

Methods to achieve entity integrity in SQL:

Entity integrity refers to ensuring that every An entity (a row of data) has a unique and non-null identifier. In SQL, entity integrity can be achieved using the following methods:

Primary key constraints:

• Primary key constraints specify one or more columns in the table that can Uniquely identifies each row in the table.
• Syntax: PRIMARY KEY (column_name(s))

##Unique constraint:

Unique A constraint specifies one or more columns in a table whose values ​​must be unique within the table.
• Syntax:
• UNIQUE (column_name(s))

##Non-empty constraints:

Not A null constraint ensures that a specific column in a table cannot contain null values.

• Syntax:
NOT NULL

Example:

Suppose there is a class named

Students

table with the following columns:

id
name
age
To achieve entity integrity, we can add the following constraints:

PRIMARY KEY (id)
• : Ensure id The value of the column uniquely identifies each row of students.
UNIQUE (name)
• : Ensure that the value of the name column is unique in the table.
NOT NULL (id, name)
• : Ensure that the id and name columns cannot contain null values.
These constraints will ensure that:

Every student in the database has a unique identifier (

id
• ). No two students have the same name (
name
• ). Student information does not contain any null values.

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