奇怪的MySQL查询计划:为什么这个查询使用临时&filesort? 如何优化它?
我有一个查询: SELECT * FROM amp_ads,amp_c,amp_c_countries WHERE (amp_c.zone = '24' OR amp_c.zone = '25') AND amp_ads.ad_complete = '1' AND amp_ads.ad_type = '17' AND amp_ads.accept = '1' AND amp_ads.en_w = '1' AND amp_c.en_u = '1' AND amp_c.en_w = '1' AND (amp_c.i_nu>'0' OR amp_c.c_nu>'0' OR amp_c.d_valid_by>'1299341823' OR amp_c.unlimit='1') AND (amp_c.i_d_max='0' OR amp_c.i_d_nu>'0') AND (amp_c.c_d_max='0' OR amp_c.c_d_nu>'0') AND amp_c.t1<'1299341823' […]