2平日（月〜金）の統計

Question

私は以下のものをPostgres 9.5.4データベースに格納しています。

CREATE TABLE activity (
    id int primary key, 
    cat_id smallint, 
    start_date date, 
    end_date date 
); 

INSERT INTO activity VALUES(5822, 1, '2016-07-01', '2016-07-01'); 
INSERT INTO activity VALUES(5824, 5, '2016-07-01', '2016-07-01'); 
INSERT INTO activity VALUES(5825, 4, '2016-07-01', '2016-07-01'); 
INSERT INTO activity VALUES(5840, 5, '2016-07-01', '2016-07-01'); 
INSERT INTO activity VALUES(5873, 5, '2016-07-05', '2016-07-05'); 
INSERT INTO activity VALUES(5875, 3, '2016-07-05', '2016-07-05'); 
INSERT INTO activity VALUES(5876, 5, '2016-07-05', '2016-07-05'); 
INSERT INTO activity VALUES(5882, 5, '2016-07-05', '2016-07-05'); 
INSERT INTO activity VALUES(5883, 5, '2016-07-05', '2016-07-05'); 
INSERT INTO activity VALUES(5888, 4, '2016-07-05', '2016-07-05'); 
INSERT INTO activity VALUES(5905, 4, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5908, 5, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5911, 5, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5912, 3, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5913, 4, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5915, 4, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5920, 4, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5923, 4, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5928, 5, '2016-07-06', '2016-07-06'); 
INSERT INTO activity VALUES(5949, 4, '2016-07-07', '2016-07-07'); 
INSERT INTO activity VALUES(5955, 5, '2016-07-07', '2016-07-07'); 
INSERT INTO activity VALUES(5959, 4, '2016-07-07', '2016-07-07'); 
INSERT INTO activity VALUES(5960, 2, '2016-07-07', '2016-07-07'); 
INSERT INTO activity VALUES(5965, 4, '2016-07-07', '2016-07-07'); 
INSERT INTO activity VALUES(5998, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6000, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6001, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6003, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6005, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6008, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6012, 4, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6016, 5, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6018, 5, '2016-07-11', '2016-07-11'); 
INSERT INTO activity VALUES(6032, 4, '2016-07-12', '2016-07-12'); 
INSERT INTO activity VALUES(6035, 5, '2016-07-12', '2016-07-12'); 
INSERT INTO activity VALUES(6052, 4, '2016-07-12', '2016-07-12'); 
INSERT INTO activity VALUES(6060, 4, '2016-07-12', '2016-07-12'); 
INSERT INTO activity VALUES(6070, 5, '2016-07-13', '2016-07-13'); 
INSERT INTO activity VALUES(6075, 5, '2016-07-13', '2016-07-11'); 
INSERT INTO activity VALUES(6076, 3, '2016-07-13', '2016-07-11'); 
INSERT INTO activity VALUES(6077, 5, '2016-07-13', '2016-07-11'); 
INSERT INTO activity VALUES(6078, 5, '2016-07-13', '2016-07-13'); 

2つの稼働日（月曜日から金曜日のみ）の違いに関する統計をいくつか収集したいと思います。

このクエリは、私が達成しようとしているものを助けるかもしれません。

SELECT 
    SUM(CASE WHEN cat_id = 5 THEN 1 ELSE 0 END) as "# Cat 5", 
    AVG(CASE WHEN cat_id = 5 THEN start_date - end_date END) as "AVG Cat 5", 
    MIN(CASE WHEN cat_id = 5 THEN start_date - end_date END) as "MIN Cat 5", 
    MAX(CASE WHEN cat_id = 5 THEN start_date - end_date END) as "MAX Cat 5" 
FROM activity 

また、私はSQL Fiddleを作成しました。これはテストに役立ちます。

これをさらに説明すると、土曜日にアクティビティが作成され、月曜日に完了したとすると、期間は0日（土曜日と日曜日は含まれないため）です。アクティビティが金曜日に作成され、月曜日に完了した場合、その期間は1になります。

ありがとうございます。

Answer 1

あなたがここで何をしようとしているのかは、CTEを使用してプレーンSQLで行うことができます。日付から特定の日数離れた営業日を計算する場合は、this answerを参照してください。逆の操作が必要ですが、その点が分かります。

それは、簡単かつ迅速であるが、しかし、2つの日付の間の平日の数を計算するために上記のリンクの答えから作り直しこの機能を使用する：

CREATE FUNCTION business_days_between(from_date date, to_date date) RETURNS int AS $$ 
-- This function assumes Mon-Fri business days. This returns an "open" range of days, 
-- i.e. from Monday to Tuesday = 1. For a "closed" range of days (e.g. rentals), you 
-- should add 1 to the result. 
DECLARE 
    alldays int; -- All calendar days in the period, counting down to 0 
    days  int; -- The working days to calculate, counting up from 0 
    weeks  int; 
    start_dow int; 
    temp_date date; 
BEGIN 
    -- If from_date = to_date simply return 0. 
    IF from_date = to_date THEN 
    RETURN 0; 
    END IF; 

    -- If dates are reversed, flip them 
    IF from_date > to_date THEN 
    temp_date := from_date; 
    from_date = to_date; 
    to_date := temp_date; 
    END IF; 

    -- Set up variables, remove initial weekend days 
    alldays := to_date - from_date; 
    start_dow := extract(dow from from_date); 
    IF start_dow = 0 THEN -- Don't count initial Sunday 
    alldays := alldays - 1; 
    END IF; 
    IF start_dow = 6 THEN -- Fudge initial Saturday to the following Sunday 
    start_dow := 0; 
    alldays := alldays - 2; 
    END IF; 
    IF alldays <= 0 -- from_date is Saturday, to_date is next Sunday or Monday 
    RETURN 0; 
    END IF; 

    -- Process the current week 
    IF start_dow + alldays <= 5 THEN -- Stay in this week 
    RETURN alldays; 
    ELSE        -- Count towards Friday 
    days := 5 - start_dow; 
    alldays := alldays - days; 
    END IF; 

    -- Move by full weeks 
    weeks := alldays/7; 
    alldays := alldays - weeks * 7; 
    days := days + weeks * 5; 

    -- Add any remaining days, after the weekend 
    IF alldays > 2 THEN 
    days := days + alldays - 2; 
    END IF; 

    RETURN days; 
END; $$ LANGUAGE plpgsql STRICT IMMUTABLE; 

をあなたのクエリは現在次のようになります。

SELECT 
    count(*) as "# Cat 5", 
    avg(business_days) AS "AVG Cat 5", 
    min(business_days) AS "MIN Cat 5", 
    max(business_days) AS "MAX Cat 5" 
FROM (
    SELECT business_days_between(start_date, end_date) AS business_days 
    FROM activity 
    WHERE cat_id = 5) sub;