Zabbix history max value

#!/bin/bash

start_daytime=$(date --date "$1 00:00:00" +%s)
end_daytime=$(date --date "$2 00:00:00" +%s)
itemid=${3:-23347}
itemid="'"$itemid"'"

sql_string="select * from history where value = \
        ( select max(value) from history where itemid=$itemid and \
        clock >= $start_daytime and clock <= $end_daytime) \
        and itemid=$itemid and clock >= $start_daytime and clock <= $end_daytime"

mysql -B -s -u root -p zabbix -e "$sql_string"