mysql删除多个重复数据，多个字段添加唯一性索引

需求：删除station_id、ab_data_time、item_code_id、data_cycle、ab_value 字段重复的记录

#查询重复的数据

select
  b.id,b.station_id,b.ab_data_time,b.item_code_id,b.data_cycle,b.ab_lable,b.ab_value
from
d_abnormal_data_yyyymms b
where
(b.station_id,b.ab_data_time,b.item_code_id,b.data_cycle,b.ab_value) in (
    select *
    from
    (
    select
        station_id,ab_data_time,item_code_id,data_cycle,ab_value
     from
         d_abnormal_data_yyyymms
      group by
          station_id,ab_data_time,item_code_id,data_cycle,ab_value
      having
          count(*) >1
    ) b
)
and ab_data_time <= '2019-01-22 12:00:00';

#删除多个字段重复数据(去掉ab_lable字段)

delete
from
d_abnormal_data_yyyymms
where
(station_id,ab_data_time,item_code_id,data_cycle,ab_value) in (
    select *
    from
    (
    select
        station_id,ab_data_time,item_code_id,data_cycle,ab_value
     from
         d_abnormal_data_yyyymms
      group by
          station_id,ab_data_time,item_code_id,data_cycle,ab_value
      having
          count(*) >1
    ) b
)
and 

ab_data_time <= '2019-01-22 12:00:00'

and

id not in

(select * from 

(select
min(id)
from
	d_abnormal_data_yyyymms
where 

ab_data_time <=  '2019-01-22 12:00:00' 

group by
	station_id,ab_data_time,item_code_id,data_cycle,ab_value
having count(*)>1)c
);

　　

#查看数据是否还保留一条

select
  b.id,b.station_id,b.ab_data_time,b.item_code_id,b.data_cycle,b.ab_lable,b.ab_value
from
d_abnormal_data_yyyymms b
where
ab_data_time = '2018-12-17 11:50:00';

#添加唯一索引

create unique index station_id_time_code_cycle_lable_value on d_abnormal_data_yyyymms(station_id,ab_data_time,item_code_id,data_cycle,ab_lable,ab_value);