mysql中修改关联变量条件、数据查询及显示成一行的相关操作
本篇文章给大家主要讲的是关于MySQL中修改关联变量条件、数据查询及显示成一行的相关操作的内容,感兴趣的话就一起来看看这篇文章吧,相信看完mysql中修改关联变量条件、数据查询及显示成一行的相关操作对大家多少有点参考价值吧。
10年积累的做网站、网站建设经验,可以快速应对客户对网站的新想法和需求。提供各种问题对应的解决方案。让选择我们的客户得到更好、更有力的网络服务。我虽然不认识你,你也不认识我。但先做网站后付款的网站建设流程,更有宿迁免费网站建设让你可以放心的选择与我们合作。
一对多数据显示成一行
GROUP_CONCAT(expr)
1、涉及的表关系:teacher表、teacher_subject_rel表(教师所能教的学科表)、subject表
2、业务场景: 需要拉取所有教师的编号(teacher_no)、学科名(subject_name)。   教师表(teacher)和学科(teacher_subject_rel)是一对多关系, 往往查询出现的是同一教师多条 数据。我们希望得到每个教师一条数据 学科拼接成一条
1、基本语法
group_concat( [DISTINCT] 要连接的字段 [Order BY 排序字段 ASC/DESC] [Separator '分隔符'] )
2、例子
SELECT t.teacher_id as '教师id', t.teacher_no '教师编号', ( SELECT GROUP_CONCAT(s.subject_name) FROM teacher_subject_rel tsr LEFT JOIN `subject` s ON tsr.subject_id = s.subject_id WHERE t.teacher_id = tsr.teacher_id ) AS '学科' FROM teacher t
子查询、查询临时表、EXISTS
例子
SELECT * FROM ( SELECT o.id, o.student_intention_id, s. NAME, s.area_id, a.area_name, s.exam_year, o. STATUS, CASE o. STATUS WHEN '1' THEN '待提交' WHEN '2' THEN '待指派' WHEN '3' THEN '已完成' WHEN '4' THEN '处理中' END statusName, CASE o.emergency_degree WHEN '1' THEN '正常' WHEN '2' THEN '紧急' WHEN '3' THEN '非常紧急' END emergencyDegreeName, o.emergency_degree, o.update_time, ( SELECT first_lesson_time FROM jx_strategy WHERE jx_lesson_plan_order_id = o.id AND STATUS IN (2, 7) AND first_lesson_time > now() ORDER BY first_lesson_time ASC LIMIT 1 ) AS first_time, ( SELECT deal_user_id FROM jx_strategy WHERE jx_lesson_plan_order_id = o.id AND STATUS <> 7 AND deal_user_id <> 0 ORDER BY id DESC LIMIT 1 ) AS deal_user_id FROM jx_lesson_plan_order o LEFT JOIN student s ON s.student_intention_id = o.student_intention_id LEFT JOIN area a ON s.area_id = a.id WHERE o. STATUS <> 1 AND s.phone = '18501665888' AND o.emergency_degree = 1 AND o. STATUS = 2 AND s.exam_year = '2015' AND o.update_time >= '2018-08-14 20:28:55' AND o.update_time <= '2018-08-14 20:28:55' ) AS a WHERE 1 = 1 AND a.deal_user_id = 145316 AND a.first_time >= '2018-08-17 00:00:00' AND a.first_time <= '2018-08-30 00:00:00' AND EXISTS ( SELECT * FROM jx_strategy js WHERE js.jx_lesson_plan_order_id = a.id AND js. STATUS IN (2, 7) AND js.subject_id IN (2, 3) ) ORDER BY a.update_time DESC LIMIT 0, 10
update 关联变量条件修改
1、涉及的表关系: user_info表中的 id_number(身份证号) teacher表中的birth字段、 关联关系usrer_id = teacher_id
2、业务场景:获取用户身份证上的出生日期将出生日期更新在birth字段
UPDATE teacher t INNER JOIN ( SELECT t.teacher_id, t.birth, u.id_number, CONCAT(SUBSTRING(u.id_number, 7, 4), '-', SUBSTRING(u.id_number, 11, 2), '-', SUBSTRING(u.id_number, 13, 2)) as birth2, u.reg_date, t.exit_time from teacher t INNER JOIN user_info u ON u.user_id = t.teacher_id ) info on info.teacher_id = t.teacher_id SET t.birth = info.birth2 WHERE info.reg_date > '2018-08-20 00:00:00' and info.id_number is not NULL and (info.birth is NULL or t.birth = '') and t.is_train = 1
以上关于mysql中修改关联变量条件、数据查询及显示成一行的相关操作详细内容,对大家有帮助吗?如果想要了解更多相关,可以继续关注我们的行业资讯板块。
分享题目:mysql中修改关联变量条件、数据查询及显示成一行的相关操作
本文地址:http://pwwzsj.com/article/gjhoeh.html