idselect_typetablepartitionstypepossible_keyskeykey_lenrefrowsfilteredExtra
1SIMPLErcNULLALLNULLCONSTRAINT_SCHEMA,TABLE_NAMENULLNULLNULLNULLUsing where; Open_full_table; Scanned 0 databases
1SIMPLEkcuNULLALLNULLTABLE_SCHEMA,TABLE_NAMENULLNULLNULLNULLUsing where; Open_full_table; Scanned 0 databases; Using join buffer (Block Nested Loop)