我想在mysql中計算不同的值。MySql中的獨特計數
select
bank_sample_map.sample_track_id,sample_details.sample_id,order_number, order_details.sample_detail_id
from
bank_sample_map
left join
sample_details on bank_sample_map.sample_track_id = sample_details.sampletrack_id
left join
order_details on order_details.sample_detail_id = sample_details.sample_id
where
sample_detail_id = 559662
它返回
雖然具有鮮明的查詢,它返回2行
select
DISTINCT(bank_sample_map.sample_track_id),sample_details.sample_id,order_number, order_details.sample_detail_id
from
bank_sample_map
left join
sample_details on bank_sample_map.sample_track_id = sample_details.sampletrack_id
left join
order_details on order_details.sample_detail_id = sample_details.sample_id
where
sample_detail_id = 559662
而且,當我試圖把數,則返回6.但我需要計數2.
你是如何考慮的計數? – mikeyq6