날짜 비교

SQL로 리포트 만들기

Tyler Pernes

Learning & Development Consultant

답해야 할 질문

지난달 vs 전달?
7일 이동?

original_table
+------------+----------+
| date       | revenue  |
|------------+----------|
| 2018-01-01 | 400      |
| 2018-01-02 | 380      |
| 2018-01-03 | 625      |
+------------+----------+

월별 증감 비교

LAG(value, offset): 현재 행에서 이전 offset행의 value 반환
LEAD(value, offset): 현재 행에서 다음 offset행의 value 반환

월별 증감 비교

1단계: 월별 매출 표시

SELECT
    DATE_PART('month',date) AS month,
    SUM(revenue) as current_rev
FROM original_table
GROUP BY month;

2단계: 전달 매출

SELECT
    DATE_PART('month',date) AS month,
    SUM(revenue) as current_rev,
    LAG(SUM(revenue)) OVER (ORDER BY DATE_PART('month',date)) AS prev_rev
FROM original_table
GROUP BY month;

월별 증감 비교

3단계: 증감률 계산

SELECT
    DATE_PART('month',date) AS month,
    SUM(revenue) as current_rev,
    LAG(SUM(revenue)) OVER (ORDER BY DATE_PART('month',date)) AS prev_rev,
    SUM(revenue)
    /
    LAG(SUM(revenue)) OVER (ORDER BY DATE_PART('month',date))-1 AS perc_change
FROM original_table
GROUP BY month;

월별 증감 비교

3단계: 증감률 계산

+--------+--------------+-----------+--------------+
| month  | current_rev  | prev_rev  | perc_change  |
|--------+--------------+-----------+--------------|
| 01     | 15000        | null      | null         |
| 02     | 14000        | 15000     | -.06         |
| 03     | 21000        | 14000     | .50          |
+--------+--------------+-----------+--------------+

이동 계산

7개 행만 고려

새 절: ROWS BETWEEN

SUM(value) OVER (ORDER BY value ROWS BETWEEN N PRECEDING AND CURRENT ROW)

이동 계산

이동 합계 쿼리

SELECT 
    date,
    SUM(SUM(revenue)) OVER 
    (ORDER BY date ROWS BETWEEN 6 PRECEDING AND CURRENT ROW) AS weekly_revenue
FROM original_table
GROUP BY date;

새 테이블: web_data

web_data
+------------+-------------+--------+
| date       | country_id  | view   |
|------------+-------------+--------|
| 2018-01-01 | 1           | 24313  |
| 2018-01-01 | 2           | 3768   |
| 2018-01-01 | 3           | 26817  |
+------------+-------------+--------+

Ayo berlatih!

SQL로 리포트 만들기