Group by, improve SQL running speed, groupsql

Group by, improve SQL running speed, groupsql

Data Table dh_order_detail contains a total of 169247 data records.

Original SQL

SELECTFROM_UNIXTIME (order_time, '% H: % I') 'time', city, district, LEFT (company, 6) company, goods_num, order_price, order_code, order_timeFROMdh_order_detailWHEREprovince_id = 16 group by order_codeORDER BYorder_time DESCLIMIT 50

Running time more than 4 seconds

Improvement: Move group by outside

SELECT * FROM (SELECTFROM_UNIXTIME (order_time, '% H: % I') 'time', city, district, LEFT (company, 6) company, goods_num, order_price, order_code, order_timeFROMdh_order_detailWHEREprovince_id = 16 ORDER BYorder_time DESCLIMIT 50) oGROUP BYorder_code

Running time: 0.049 seconds