我遇到了MySQL的ROLLUP问题,并处理了由此产生的NULL。 IFNULL / COALESCE函数适用于普通列,但在与日期函数一起使用时似乎会崩溃。示例如下:
SELECT
YEAR(date_time) AS Year,
count(x) AS Count
FROM mytable
GROUP BY year WITH ROLLUP
返回(按预期方式)
Year Count
---- -----
2015 3
2016 2
NULL 5
当我查询非日期列(例如varchar)时,我可以使用IFNULL或COALESCE函数来处理NULL值,以用字符串替换NULL值。但是,当我将相同的逻辑应用于上述查询时,它似乎不起作用。
SELECT
COALESCE(YEAR(date_time), 'moo') AS Year,
count(x) AS Count
FROM mytable
GROUP BY year WITH ROLLUP
或
SELECT
IFNULL(YEAR(date_time), 'moo') AS 'year',
count(x) AS Count
FROM mytable
GROUP BY year WITH ROLLUP
返回
Year Count
---- -----
2015 3
2016 2
NULL 5
而非预期
Year Count
---- -----
2015 3
2016 2
moo 5
任何想法,建议?
答案 0 :(得分:2)