Database Relation Constraints Analysis

This solution analyzes the properties of the $Person$ and $Customer$ relations based on the provided schema definitions to determine the correctness of the given statements.

Statement Analysis

• Statement 1 Analysis: $aadhaar$ as Candidate Key in $Customer
  The $Customer$ relation defines $email$ as the $PRIMARY KEY. Candidate keys are columns or sets of columns that uniquely identify rows and could serve as a primary key. Since $aadhaar$ is only defined as a $FOREIGN KEY and lacks a $UNIQUE or $PRIMARY KEY constraint in the $Customer$ table, it is not a candidate key. Incorrect.
• Statement 2 Analysis: $phone$ NULLability in $Customer
  The $phone$ column in the $Customer$ relation is defined as $CHAR(10). In SQL, columns typically allow $NULL$ values by default unless a $NOT NULL constraint is explicitly applied. As there is no $NOT NULL constraint on $phone$, it can accept $NULL$ values. Correct.
• Statement 3 Analysis: $aadhaar$ as Candidate Key in $Person
  In the $Person$ relation, $aadhaar$ is declared as the $PRIMARY KEY. By definition, a $PRIMARY KEY uniquely identifies each record and must contain unique, non-NULL values. Therefore, $aadhaar$ satisfies the criteria for a candidate key. Correct.
• Statement 4 Analysis: $aadhaar$ NULLability in $Person
  $aadhaar$ is designated as the $PRIMARY KEY for the $Person relation. A fundamental property of a $PRIMARY KEY$ is that it cannot contain $NULL values. Hence, $aadhaar$ cannot be $NULL in the $Person relation. Incorrect.

Correct Statements Identification

The analysis identifies statements concerning the allowance of NULL values for the 'phone' field in the 'Customer' table and the status of 'aadhaar' as a candidate key in the 'Person' table as accurate based on standard SQL rules and the provided schema.