CREATE TABLE IF NOT EXISTS t_visit (
    id          BIGINT PRIMARY KEY AUTO_INCREMENT,
    hospital_id INT,
    creatime    DATETIME,
    visit_num   INT
);

SELECT
    SUM(visit_num)
FROM t_visit
WHERE WEEKDAY(creatime) < 5;

WEEKDAY(creatime)

type: ALL
rows: 全表行數(shù)

CREATE INDEX idx_visit_creatime ON t_visit(creatime);

EXPLAIN
SELECT
    SUM(visit_num)
FROM t_visit
WHERE 
    creatime >= '2025-01-01'
    AND creatime <  '2025-02-01'
    AND WEEKDAY(creatime) < 5;
		EXPLAIN
SELECT
    SUM(visit_num)
FROM t_visit FORCE INDEX (idx_visit_creatime)
WHERE 
    creatime >= '2025-01-01'
    AND creatime <  '2025-02-01'
    AND WEEKDAY(creatime) < 5;

ALTER TABLE t_visit
  ADD COLUMN weekday TINYINT AS (WEEKDAY(creatime)) STORED,
  ADD COLUMN is_workday TINYINT(1) AS (
    CASE WHEN WEEKDAY(creatime) < 5 THEN 1 ELSE 0 END
  ) STORED,
  ADD INDEX idx_visit_workday (is_workday, creatime);

CREATE TABLE dim_date (
    date_key    DATE PRIMARY KEY,
    weekday     TINYINT,
    is_workday  TINYINT,
    is_holiday  TINYINT,
    holiday_name VARCHAR(20)
);

ALTER TABLE t_visit
  ADD COLUMN visit_date DATE AS (DATE(creatime)) STORED,
  ADD INDEX idx_visit_date (visit_date);

SELECT
    v.hospital_id,
    SUM(v.visit_num) AS total_visit
FROM t_visit v
JOIN dim_date d
    ON v.visit_date = d.date_key
WHERE 
    d.is_workday = 1
    AND v.visit_date BETWEEN '2025-01-01' AND '2025-02-01'
GROUP BY v.hospital_id;

SELECT
    v.hospital_id,
    d.is_workday,
    SUM(v.visit_num) AS visit_total,
    COUNT(*) AS visit_times
FROM t_visit v
JOIN dim_date d
    ON v.visit_date = d.date_key
WHERE
    v.visit_date >= '2025-01-01'
    AND v.visit_date <  '2025-02-01'
    AND d.is_workday = 1       -- 只算工作日
GROUP BY v.hospital_id, d.is_workday
ORDER BY hospital_id;