如何在mysql上编写查询，该查询将计算用户这次访问应用程序的连续多少天

Question

我有这样的表：

CREATE TABLE Activity (LoginDate DATE, ID int);                             

INSERT INTO Activity VALUES
    ("2016-10-01", 2), ("2016-10-01", 1), ("2016-10-02", 1), ("2016-10-02", 3), 
    ("2016-10-03", 1), ("2016-10-03", 3), ("2016-10-04", 2), ("2016-10-05", 1);

并且需要接收如下内容： table

 <table><tbody><tr><th>Date</th><th>UserID</th><th>Days in Row</th></tr><tr><td>2016-10-01</td><td>2</td><td>0</td></tr><tr><td>2016-10-01</td><td>1</td><td>0</td></tr><tr><td>2016-10-02</td><td>1</td><td>1</td></tr><tr><td>2016-10-02</td><td>3</td><td>0</td></tr><tr><td>2016-10-03</td><td>1</td><td>2</td></tr><tr><td>2016-10-03</td><td>3</td><td>1</td></tr><tr><td>2016-10-04</td><td>2</td><td>0</td></tr><tr><td>2016-10-05</td><td>1</td><td>0</td></tr></tbody></table> 

仅使用sql或t-sql，不使用CTE。 有任何想法吗？

Answer 1

我没有MySQL，因此更多地将其视为伪代码。 这样的事情对您有用吗？

CREATE PROCEDURE TrackConsecutiveVisits()
     BEGIN

     CREATE TABLE Activity_Results (LoginDate DATE, ID int, con_visits int);

     DECLARE con_visit INTEGER DEFAULT 0;

     DECLARE last_id INTEGER DEFAULT 0;
     DECLARE last_date DATE DEFAULT "1900-01-01";
     DECLARE cur_id INTEGER DEFAULT 0;
     DECLARE cur_date DATE DEFAULT "1900-01-01";

     DECLARE concur CURSOR FOR 
         SELECT ID,
                LoginDate
           FROM Activity
          ORDER
             BY id,
                loginDate;

    OPEN con_cursor;

    con_loop: LOOP
        FETCH concur INTO cur_id, cur_date;

        IF last_id = cur_id AND last_date + 1 = cur_date THEN
            SET con_visit = con_visit + 1
        ELSE
            SET con_visit = 0
        END IF

        INSERT INTO Activity_Results VALUES (cur_id, cur_date, con_visit)

        SET last_id = cur_id;
        SET last_date = cur_date;

    END LOOP

    CLOSE concur

END;