2006 - MySQL server has gone away

select sum(tax_rate) as tax_rate from tax_rates tr left join zones_to_geo_zones za on (tr.tax_zone_id = za.geo_zone_id) left join geo_zones tz on (tz.geo_zone_id = tr.tax_zone_id) where (za.zone_country_id is null or za.zone_country_id = '0' or za.zone_country_id = '81') and (za.zone_id is null or za.zone_id = '0' or za.zone_id = '82') and tr.tax_class_id = '1' group by tr.tax_priority

[XT SQL Error]

2006 - MySQL server has gone away

select count(*) as total from sessions where sesskey = 'urh7027tfu7m1un2ik00rlr995'

[XT SQL Error]