一段shell的tips

#! /bin/sh

if [ -f test.sql ];then
   rm -f test.sql
fi

touch test.sql

for (( i=0;i<1000;i++))
do
   mc='insert into t_user(user_name,user_number) values '
   for (( j=0;j<1000;j++))
   do
     num=$((15500000000+$i*1000+j))
     name=$i"t"$j
     if [ $j != 999 ];then
         mc=$mc"('$name',$num),"
     else
         mc=$mc"('$name',$num);"
     fi
   done
   echo $mc >> test.sql
done