**Core Statistical Functions:**

-- Standard deviation and variance

SELECT

department,

AVG(salary) as avg_salary,

STDDEV(salary) as salary_stddev,

VARIANCE(salary) as salary_variance

FROM employees

GROUP BY department;

-- Correlation between two variables

SELECT

CORR(years_experience, salary) as experience_salary_correlation

FROM employees;

**Distribution Functions:**

-- Percentile rank (0 to 1)

SELECT

name,

salary,

PERCENT_RANK() OVER (ORDER BY salary) as percentile_rank

FROM employees;

-- Cumulative distribution

SELECT

name,

salary,

CUME_DIST() OVER (ORDER BY salary) as cumulative_dist

FROM employees;

-- Specific percentile values

SELECT

PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY salary) as median,

PERCENTILE_CONT(0.75) WITHIN GROUP (ORDER BY salary) as q3,

PERCENTILE_CONT(0.9) WITHIN GROUP (ORDER BY salary) as p90

FROM employees;

**Advanced Patterns:**

-- Multiple functions with window frames

SELECT

date,

sales,

STDDEV(sales) OVER (

ORDER BY date

ROWS BETWEEN 6 PRECEDING AND CURRENT ROW