Question

我想我太累了或者什么......在这里看不出任何坏事。

DROP TABLE IF EXISTS time_dimension;

CREATE TABLE time_dimension (
        id                      INTEGER PRIMARY KEY,  -- year*10000+month*100+day
        db_date                 DATE NOT NULL,
        year                    INTEGER NOT NULL,
        month                   INTEGER NOT NULL, -- 1 to 12
        day                     INTEGER NOT NULL, -- 1 to 31
        quarter                 INTEGER NOT NULL, -- 1 to 4
        week                    INTEGER NOT NULL, -- 1 to 52/53
        day_name                VARCHAR(9) NOT NULL, -- 'Monday', 'Tuesday'...
        month_name              VARCHAR(9) NOT NULL, -- 'January', 'February'...
        holiday_flag            CHAR(1) DEFAULT 'f' CHECK (holiday_flag in ('t', 'f')),
        weekend_flag            CHAR(1) DEFAULT 'f' CHECK (weekday_flag in ('t', 'f')),
        event                   VARCHAR(50),
        UNIQUE td_ymd_idx (year,month,day),
        UNIQUE td_dbdate_idx (db_date)

) Engine=MyISAM;

DROP PROCEDURE IF EXISTS fill_date_dimension;
DELIMITER //
CREATE PROCEDURE fill_date_dimension(IN startdate DATE,IN stopdate DATE)
BEGIN
    DECLARE currentdate DATE;
    SET currentdate = startdate;
    WHILE currentdate < stopdate DO
        INSERT INTO time_dimension VALUES (
                        YEAR(currentdate)*10000+MONTH(currentdate)*100 + DAY(currentdate),
                        currentdate,
                        YEAR(currentdate),
                        MONTH(currentdate),
                        DAY(currentdate),
                        QUARTER(currentdate),
                        WEEKOFYEAR(currentdate),
                        DATE_FORMAT(currentdate,'%W'),
                        DATE_FORMAT(currentdate,'%M'),
                        'f',
                        CASE DAYOFWEEK(currentdate) WHEN 1 THEN 't' WHEN 7 then 't' ELSE 'f' END,
                        NULL);
        SET currentdate = ADDDATE(currentdate,INTERVAL 1 DAY);
    END WHILE;
END
//
DELIMITER ;

TRUNCATE TABLE time_dimension;

CALL fill_date_dimension('2000-01-01','2018-01-01');

问题是为什么project_id会给我0？

P.S。在数据库中，我确实完全插入了我的项目表，是的，我仔细检查了要求的值。

Answer 1

将代码更改为

while(rs.next()) {
       int project_id = rs.getInt("project_id");
        System.out.println(project_id);
}

我猜你会看到没有值（如果project_key有问题）

或许多值，最后一个将为零！

Answer 2

尝试以下代码以查看结果集是否返回任何值

rs.first();
System.out.println(rs.getInt("project_id"));

如果您没有看到任何值，则表示问题与查询有关。没有返回任何内容，并且该集合为空。（我打算对此发表评论，但我没有足够的声誉）

为什么ResultSet在执行后返回0值？

2 个答案: