explain someSql;
possible_keys show useable keys
explain select a from b use index (c) where xxx ;
show index from tableA;
create index someIndex on someTable(someColumn);
drop index someIndex on someTable;
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: some table
partitions: NULL
type: ALL
possible_keys: PRIMARY
key: NULL
key_len: NULL
ref: NULL
rows: 2972
filtered: 1.11
Extra: Using where