Question

So my expertise is not in MySQL so I wrote this query and it is starting to run increasingly slow as in 5 minutes or so with 100k rows in EquipmentData and 30k or so in EquipmentDataStaging (which to me is very little data):

   CREATE TEMPORARY TABLE dataCompareTemp 
   SELECT eds.eds_id FROM equipmentdatastaging eds
   INNER JOIN equipment e ON e.e_id_string = eds.eds_e_id_string
   INNER JOIN equipmentdata ed ON e.e_id = ed.ed_e_id 
       AND eds.eds_ed_log_time=ed.ed_log_time 
       AND eds.eds_ed_unit_type=ed.ed_unit_type
       AND eds.eds_ed_value = ed.ed_value

I am using this query to compare data rows pulled from a clients device to current data sitting within their database. From here I take the temp table and use the ID’s off it to make conditional decisions. I have the e_id_string indexed and I have e_id indexed and everything else is not. I know that it looks stupid that I have to compare all this information, but the clients system is spitting out redundant data and I am using this query to find it. Any type of help on this would be greatly appreciated whether it be a different approach by SQL or MySql Management. I feel like when I do stuff like this in MSSQL it handles the requests much better, but that is probably because I have something set up incorrectly.

Answer 1

TIPS

• index all necessary columns which are using with ON or WHERE condition
  here you need to index eds_ed_log_time,eds_e_id_string, eds_ed_unit_type, eds_ed_value,ed_e_id,ed_log_time,ed_unit_type,ed_value

• change syntax to SELECT STRAIGHT JOIN … see more reference