query for max date value for each item in a WHERE IN clause

[kaf3773]

Hello,

I am trying to query the data set below for the data_value for the data_id of the recent data_date.

So for data_id 18554 the recent data_date will be 2/8/2016 18:40 and its data_value will be 29504.76

And for data_id 18555 the recent data_date will be 2/8/2016 18:40 and its data_value will be -90909090909

data_id	data_name	data_date	data_value
18554	traffic_in	2/8/2016 18:30	30737.11333
18554	traffic_in	2/8/2016 18:10	31780.68
18554	traffic_in	2/8/2016 18:35	30338.82
18554	traffic_in	2/8/2016 18:15	31393.36667
18554	traffic_in	2/8/2016 18:40	29504.76
18554	traffic_in	2/8/2016 17:50	32225.28
18554	traffic_in	2/8/2016 18:00	32225.32
18554	traffic_in	2/8/2016 17:55	32240.71333
18554	traffic_in	2/8/2016 17:45	32602.98
18554	traffic_in	2/8/2016 18:20	30874.39333
18554	traffic_in	2/8/2016 18:25	30511.56
18554	traffic_in	2/8/2016 18:05	32090.84667
			
18555	traffic_in	2/8/2016 18:15	-90909090909
18555	traffic_in	2/8/2016 18:35	-90909090909
18555	traffic_in	2/8/2016 17:45	-90909090909
18555	traffic_in	2/8/2016 18:00	-90909090909
18555	traffic_in	2/8/2016 17:50	-90909090909
18555	traffic_in	2/8/2016 17:55	-90909090909
18555	traffic_in	2/8/2016 18:10	-90909090909
18555	traffic_in	2/8/2016 18:20	-90909090909
18555	traffic_in	2/8/2016 18:05	-90909090909
18555	traffic_in	2/8/2016 18:25	-90909090909
18555	traffic_in	2/8/2016 18:40	-90909090909
18555	traffic_in	2/8/2016 18:30	0.213333333

The results i want is

data_id	data_name	data_date	data_value
18554	traffic_in	2/8/2016 18:40	29504.76
18555	traffic_in	2/8/2016 18:40	-90909090909

But when i use the following MySQL statement

SELECT data_id,data_name,max(data_date),data_value FROM `data_source_` where `data_id` IN (18554,18555) AND data_name = 'traffic_in'

this just gives me

data_id	data_name	data_date	data_value
18554	traffic_in	2/8/2016 18:40	29504.76

Help will be very much appreciated.

Thanks

[hsriat]

Something's missing...

group by