mysql - 在 mysql 列中获取天数

Question

我Stored Procedure在 MySQL 中写了一个。

我试图分别在任何月份的列中获取天数。

下面是sql query

DELIMITER $$

DROP PROCEDURE IF EXISTS `GenerateReport`$$

CREATE
    DEFINER = `FreeUser`@`localhost`
    PROCEDURE `databasename`.`GenerateReport`(
    IN gDate DATE, 
    IN gUserID VARCHAR(10)
    )

    BEGIN
    DECLARE gStart INT;
    DECLARE gDays INT;
    SET gStart = 1;
    SET gDays = DAY(LAST_DAY(gDate));

    SELECT e.AssociateID, CONCAT(e.FirstName, ' ', e.MiddleName, ' ', e.LastName) AS `EmployeeName`, d.DesignationName, 
    ts.TSDate, 

    /* Trying to get days in column, Starts here */
    loopOne: LOOP
        IF gStart <= gDays THEN
            gStart = gStart + 1;
                case gStart IS NOT NULL THEN 'ItsDate' ELSE 'NoDate' END,
            ITERATE loopOne;
        END IF;
            LEAVE loopOne;
    END LOOP loopOne;
    /* Trying to get days in column, ends here */

    gStart AS `Start`, gDays AS `NoofDays`

    FROM timesheet ts
    LEFT JOIN employee e ON e.EmpID = ts.EmpID
    LEFT JOIN designation d ON d.DesignationId = e.DEsignationID
    WHERE DATE_FORMAT(ts.TSDate, '%Y-%m') = DATE_FORMAT(gDate, '%Y-%m')
    GROUP BY e.AssociateID;


    END$$

DELIMITER ;

期望的输出

考虑额外 UI 的图像，下面可能不是很好的表示

----------------------------------------------------------
AssociateID | EmployeeName | DesignationName | 1 | 2 | 3 | 4 | .... | 31 | Start | gDays
---------------------------------------------------------
    001     |John Carter    | Dae ja        |   ItsDate | ItsDate| .... | ItsDate | 1 | 31

----------------------------------------------------------------------------------  

Answer 1

以这种方式构建与循环、if 语句或任何其他流控制混合的查询是不可能的。

您需要构建一个动态准备好的语句，然后执行它。

drop procedure if exists dynamiccolumns;
delimiter //

create procedure dynamiccolumns()
    begin
        declare v_count int default 1;

        set @ps := 'select now()';
        oneToTen: loop
            if v_count = 10 then
                leave oneToTen;
            end if;

            set @ps := concat(@ps, ", ");
            set @ps := concat(@ps, v_count);

            set v_count := v_count + 1;
        end loop oneToTen;

        set @ps := concat(@ps, " from dual");

        prepare ps from @ps;
        execute ps;
        deallocate prepare ps;

        end//
delimiter ;

并称它为

mysql> call dynamiccolumns;
+---------------------+---+---+---+---+---+---+---+---+---+
| now()               | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
+---------------------+---+---+---+---+---+---+---+---+---+
| 2013-07-10 06:11:43 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
+---------------------+---+---+---+---+---+---+---+---+---+
1 row in set (0.00 sec)