需求是：有个查询最近7天的折线图，这个就要求没有数据就要补0

现在表名为：wo_work_order
时间字段为：create_time

SQL如下：

SELECT
	DATE_FORMAT( a.timeDay, '%Y-%m-%d' ) AS day,
	IFNULL( b.count, 0 ) AS count
FROM
	(
	SELECT
		curdate( ) AS timeDay UNION ALL
	SELECT
		date_sub( curdate( ), INTERVAL 1 DAY ) AS timeDay UNION ALL
	SELECT
		date_sub( curdate( ), INTERVAL 2 DAY ) AS timeDay UNION ALL
	SELECT
		date_sub( curdate( ), INTERVAL 3 DAY ) AS timeDay UNION ALL
	SELECT
		date_sub( curdate( ), INTERVAL 4 DAY ) AS timeDay UNION ALL
	SELECT
		date_sub( curdate( ), INTERVAL 5 DAY ) AS timeDay UNION ALL
	SELECT
		date_sub( curdate( ), INTERVAL 6 DAY ) AS timeDay 
	) a
	LEFT JOIN (
	SELECT
		date( d.create_time ) AS day,
		count(1) AS count
	FROM
		wo_work_order d 
		-- 在这里进行条件判断
		WHERE d.status = '关闭'
	GROUP BY
		date( d.create_time ) 
	) b ON a.timeDay = b.day 
ORDER BY
	day

结果输出如下：