Purpose
This function returns the population covariance of a set of number pairs (a type of relation measure). This equates to the following formula:
Syntax
covar_pop ::=
Usage Notes
- If either expr1 or expr2 is NULL, Exasol removes the corresponding row from the window before the computation of the function.
- For information about the over_clause and analytic functions in general, refer to the Analytic Functions section.
Examples
Aggregate Function
SELECT
department,
COVAR_POP(age, current_salary) COVAR_POP
FROM employee_table GROUP BY department;Result
| DEPARTMENT | COVAR_POP |
| ACCOUNTS | 16000 |
| HR | 45625 |
Analytic Function
SELECT
id, department, age, current_salary,
COVAR_POP(age, current_salary) OVER (PARTITION BY department ORDER BY age) COVAR_POP
FROM employee_table ORDER BY department, age;Result
| ID | DEPARTMENT | AGE | CURRENT_SALARY | COVAR_POP |
| 2003 | ACCOUNTS | 27 | 80000 | 0 |
| 2001 | ACCOUNTS | 30 | 55000 | -18750 |
| 2002 | ACCOUNTS | 32 | 65000 | -14444.444 |
| 2004 | ACCOUNTS | 42 | 70000 | 16000 |
| 2005 | ACCOUNTS | 42 | 80000 | 16000 |
| 1001 | HR | 30 | 55000 | 0 |
| 1004 | HR | 30 | 70000 | 0 |
| 1002 | HR | 34 | 70000 | 6666.6667 |
| 1003 | HR | 40 | 90000 | 45625 |
