Hi Lawrence,

EXPLAIN only works with SELECT statements. Not INSERT statements.

Take the insert wrapper off and explain your select and it will work.

explain select * from batterylog
where id in (
select A.id from batterylog A
where A.testing_date = (
select max(B.testing_date) from batterylog B
where A.brand_battery_country = B.brand_battery_country));

Best regards,
Bill