问BASH中的管道导致与db2的连接丢失

EN

# it works fine
db2 connect to <db_name> user <user> using <passwd>
while read aline
do
    tab=$(echo $aline | awk -F',' '{print $1}')
    col=$(echo $aline | awk -F',' '{print $2}')
    max_id=$(db2 -x "select count($col) from $tab")
    echo $tab   $col   $max_id
done < tab.ls


# it doesn't work because of lost DB connection
db2 connect to <db_name> user <user> using <passwd>
cat tab.lst | while read aline
do
    tab=$(echo $aline | awk -F',' '{print $1}')
    col=$(echo $aline | awk -F',' '{print $2}')
    max_id=$(db2 -x "select count($col) from $tab")
    echo $tab   $col   $max_id
done