MySQL触发器之更改：一对多情况，实践操作

情景一

A表和B表，一对多关系。B表数据只要发生更改，A表的col_a字段，就会被与A表有关联关系的B表的三个字段值的总和，进行重新赋值，即col_a=col_ba+col_bb+col_bc。

表A(user_step_group)
+--------+--------+-----------------+
| usg_id | userid | usg_total_steps |
+--------+--------+-----------------+
|      1 |   5047 |           46339 |
|      2 |   5046 |               0 |
+--------+--------+-----------------+

表B(user_step_group_member)
+---------+--------+------------+----------------+-----------------+
| usgm_id | usg_id | usgm_steps | usgm_get_steps | usgm_help_steps |
+---------+--------+------------+----------------+-----------------+
|       1 |      1 |      17134 |            500 |             377 |
|       2 |      1 |      24754 |            500 |            3074 |
+---------+--------+------------+----------------+-----------------+

触发器
DELIMITER $$

CREATE
    TRIGGER update_total_step_data AFTER UPDATE
    ON `user_step_group_member`
    FOR EACH ROW
    BEGIN
   UPDATE `user_step_group` usg, `user_step_group_member` usgm SET usg.usg_total_steps = (
       SELECT SUM(usgm.usgm_steps + usgm.usgm_get_steps + usgm.usgm_help_steps) nums FROM `user_step_group_member` usgm WHERE usgm.usg_id = usg.usg_id
   )
   WHERE usgm.usg_id = usg.usg_id;
END$$

DELIMITER ;

情景二

A表和B表，一对多关系。B表新增一行数据，A表中的字段col_a，就会被B表中与A表的有关联关系的col_b的总和，重新赋值，即col_a=col_b1+col_b2+col_b3+col_b4+col_b5

表A(user_step_group_member)
+---------+--------+--------+------------+----------------+-----------------+
| usgm_id | usg_id | userid | usgm_steps | usgm_get_steps | usgm_help_steps |
+---------+--------+--------+------------+----------------+-----------------+
|       1 |      1 |   5047 |      21218 |            500 |             377 |
|       2 |      1 |   5046 |      22692 |            500 |            3074 |
|       3 |      4 |    945 |      85771 |              0 |               0 |
+---------+--------+--------+------------+----------------+-----------------+

表B(user_step_everyday_log)
+---------+---------+--------+----------------+----------------+---------------+
| usel_id | usgm_id | userid | usel_self_step | usel_help_step | usel_get_step |
+---------+---------+--------+----------------+----------------+---------------+
|       3 |       2 |   5046 |           4406 |            374 |             0 |
|       4 |       1 |   5047 |           3561 |           8377 |             0 |
|       5 |       3 |    945 |          12883 |              0 |             0 |
+---------+---------+--------+----------------+----------------+---------------+

触发器
DELIMITER $$

CREATE
    TRIGGER update_everyday_log_to_group_member_way_update AFTER UPDATE
    ON `user_step_everyday_log`
    FOR EACH ROW
    BEGIN
   UPDATE `user_step_group_member` usgm, `user_step_everyday_log` usel SET usgm.usgm_steps = (
       SELECT SUM(usel.usel_self_step) nums FROM `user_step_everyday_log` usel WHERE usgm.usgm_id = usel.usgm_id
   )
   WHERE usgm.usgm_id = usel.usgm_id;
    END$$

DELIMITER;

情景三

A表和B表，一对多关系。A表中的字段 col_Aa，col_Ab，col_Ac，分别是B表字段 col_Ba，col_Bb，col_Bc有关联关系的数据总和，当B表新增一行数据，A表的相关数据就会重新计算一下B表的对应字段的总和，重新赋值，即 col_Aa=col_Ba1+col_Ba2+col_Ba3，col_Ab=col_Bb1+col_Bb2+col_Bb3，col_Ac同左。

表A(user_step_group_member)
+---------+--------+--------+------------+----------------+-----------------+
| usgm_id | usg_id | userid | usgm_steps | usgm_get_steps | usgm_help_steps |
+---------+--------+--------+------------+----------------+-----------------+
|       1 |      1 |   5047 |      21218 |            500 |             377 |
|       2 |      1 |   5046 |      22692 |            500 |            3074 |
|       3 |      4 |    945 |      85771 |              0 |               0 |
+---------+--------+--------+------------+----------------+-----------------+

表B(user_step_everyday_log)
+---------+---------+--------+----------------+----------------+---------------+
| usel_id | usgm_id | userid | usel_self_step | usel_help_step | usel_get_step |
+---------+---------+--------+----------------+----------------+---------------+
|       3 |       2 |   5046 |           4406 |            374 |             0 |
|       4 |       1 |   5047 |           3561 |           8377 |             0 |
|       5 |       3 |    945 |          12883 |              0 |             0 |
+---------+---------+--------+----------------+----------------+---------------+

触发器
DELIMITER $$

CREATE
    TRIGGER update_everyday_log_to_group_member_way_update AFTER UPDATE
    ON `user_step_everyday_log`
    FOR EACH ROW
    BEGIN
   UPDATE `user_step_group_member` usgm, `user_step_everyday_log` usel SET usgm.usgm_steps = (
       SELECT SUM(usel.usel_self_step) nums FROM `user_step_everyday_log` usel WHERE usgm.usgm_id = usel.usgm_id
   ),
   usgm.usgm_get_steps = (
       SELECT SUM(usel.usel_get_step) nums FROM `user_step_everyday_log` usel WHERE usgm.usgm_id = usel.usgm_id
    ),
    usgm.usgm_help_steps = (
       SELECT SUM(usel.usel_help_step) nums FROM `user_step_everyday_log` usel WHERE usgm.usgm_id = usel.usgm_id
    )
   WHERE usgm.usgm_id = usel.usgm_id;
    END$$

DELIMITER;