一对多数据显现成一行
GROUP_CONCAT(expr)
1、触及的表关联:teacher表、teacher_subject_rel表(西席所能教的学科表)、subject表
2、营业场景: 须要拉取一切西席的编号(teacher_no)、学科名(subject_name)。   西席表(teacher)和学科(teacher_subject_rel)是一对多关联, 每每查询涌现的是统一西席多条 数据。我们愿望获得每一个西席一条数据 学科拼接成一条
1、基础语法
group_concat( [DISTINCT] 要衔接的字段 [Order BY 排序字段 ASC/DESC] [Separator '分隔符'] )
2、例子
SELECT t.teacher_id as '西席id', t.teacher_no '西席编号', ( 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、查询暂时表、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 '处置惩罚中' END statusName, CASE o.emergency_degree WHEN '1' THEN '一般' WHEN '2' THEN '紧要' WHEN '3' THEN '异常紧要' 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 关联变量前提修正
1、触及的表关联: user_info表中的 id_number(身份证号) teacher表中的birth字段、 关联关联usrer_id = teacher_id
2、营业场景:猎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 birth1, 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.birth1 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
以上就是mysql中关联变量前提修正、查询以及数据显现成一行的引见的细致内容,更多请关注ki4网别的相干文章!