Aggregate

STDDEV

PostgreSQL

Menghitung standar deviasi dari sekumpulan nilai. STDDEV dan STDDEV_SAMP menggunakan sample standard deviation (n-1). STDDEV_POP menggunakan population standard deviation (n).

Tipe hasil: double precision

Syntax

SQL

STDDEV(expression)
STDDEV_SAMP(expression)
STDDEV_POP(expression)

Parameter

expressionnumericwajib

Kolom numerik yang akan dihitung standar deviasinya

Contoh Penggunaan

Standar Deviasi Sederhana

SQL

1 SELECT 
2   AVG(salary) AS avg_salary,
3   STDDEV(salary) AS stddev_salary
4 FROM employees;

Menghitung rata-rata dan standar deviasi gaji.

Hasil

avg_salary	stddev_salary
8500000.00	2500000.123

Sample vs Population

SQL

1 SELECT 
2   STDDEV_SAMP(score) AS sample_stddev,
3   STDDEV_POP(score) AS population_stddev
4 FROM test_scores;

Perbandingan sample dan population standard deviation.

Hasil

sample_stddev	population_stddev
15.8113883	14.1421356

Variabilitas per Kategori

SQL

1 SELECT 
2   category,
3   AVG(price) AS avg_price,
4   STDDEV(price) AS price_variability
5 FROM products
6 GROUP BY category
7 ORDER BY price_variability DESC;