id NULL -1 0 1 2 3 4 5 6 7 8 9 10 id facility NULL NULL -1 0 1 /L 2 A01 3 ANC 4 F01 5 FBX 6 MT 7 P 8 RV 9 SRV 10 VMT id-5 facility NULL NULL -6 -5 -4 /L -3 A01 -2 ANC -1 F01 0 FBX 1 MT 2 P 3 RV 4 SRV 5 VMT id concat(facility) NULL NULL -1 0 1 /L 2 A01 3 ANC 4 F01 5 FBX 6 MT 7 P 8 RV 9 SRV 10 VMT a max(id) b 10 10 VMT 9 9 SRV 8 8 RV 7 7 P 6 6 MT 5 5 FBX 4 4 F01 3 3 ANC 2 2 A01 1 1 /L -1 -1 0 0 NULL NULL NULL grp count(*) 0 7 1 6 FACILITY NULL /L A01 ANC F01 FBX MT P RV SRV VMT FACILITY NULL /L A01 ANC F01 FBX MT P RV SRV VMT count(*) 12 count(facility) 12 count(*) 13 count(*) 1 count(*) 0 count(*) 12 count(*) 1 count(*) 12 UserId UserId UserId UserId b 1 table type possible_keys key key_len ref rows Extra t3 index a a 5 NULL 6 Using index; Using temporary t2 index a a 4 NULL 5 Using index; Distinct t1 eq_ref PRIMARY PRIMARY 4 t2.a 1 where used; Distinct a 1 table type possible_keys key key_len ref rows Extra t1 index PRIMARY PRIMARY 4 NULL 2 Using index; Using temporary t3 ref a a 5 t1.a 10 Using index; Distinct a 1 2 1 1 name aa ab name aa ab 1 1 key_link_id link NULL NULL table type possible_keys key key_len ref rows Extra t1 index id id 4 NULL 2 Using index; Using temporary t2 index id id 8 NULL 1 Using index; Distinct t3 index id id 8 NULL 1 Using index; Distinct j_lj_t2 index id id 4 NULL 2 where used; Using index; Distinct t2_lj index id id 8 NULL 1 where used; Using index; Distinct j_lj_t3 index id id 4 NULL 2 where used; Using index; Distinct t3_lj index id id 8 NULL 1 where used; Using index; Distinct id 2 a sec_to_time(sum(time_to_sec(t))) 1 00:06:15 1 00:36:30 1 00:36:30 a sec_to_time(sum(time_to_sec(t))) 1 00:06:15 1 00:36:30 a sec_to_time(sum(time_to_sec(t))) 1 00:06:15 1 00:36:30 1 00:36:30 a sec_to_time(sum(time_to_sec(t))) 1 00:06:15 1 00:36:30