Shell script "< < EOF" my purpose and problems

I understand it ：<< EOF … EOF It is mainly used to send batch internal execution statements to external commands , such as mysql, such as Oracle

mysql:

#!/bin/sh
mysql -uroot -p123456 <<EOF use test; select * from testaa while a=10000; exit EOF

Oracle

#!/bin/bash
#Filename：do.sh
su - oracle -c " export ORACLE_SID=orcl sqlplus /nolog << EOF connect / as sysdba startup; exit; EOF"
sleep 5
su - oracle -c
lsnrctl start

For example, I did this to mysql Sent an execution action , save xxx

$MYSQL db-monitor -u root << EOF delete from process; update application set run_status=0, ins_count=0; select concat(application_name,':',server_port) comp from tbl_application order by id; EOF

however , Inside this Whether the output of the execution statement can be in shell Read in , I don't know !!!...

A note ：

At the end of the EOF Write on a single line , And there should be no blank space in front , It seems that there should be no blank space behind . Accustomed to indenting left and right , hold << EOF Written in a function or loop , Attention should be paid to the .

Whether to combine commands and compare them

while [" Primary cycle "]; do
  while ["2 Stage cycle "]; do
#  Separately SQL
# sql1="INSERT INTO process ( pid, application_name,server_port,listen_port, xmx) VALUES "
# sql2="(${pid},'${app_name}',${server_port}, '${net_port:1}', '${Xmx}')"
# 
# $MYSQL -uroot doorbell-monitor -e "${sql1} ${sql2}"
#
# $MYSQL -uroot db-monitor -e "update tbl_application set run_status=1, ins_count=ins_count+1 where application_name='$app_name' and server_port='$server_port'"
# 

#  Combined execution 
    $MYSQL db-monitor -u root << EOF INSERT INTO process ( pid, application_name,server_port,listen_port, xmx) VALUES (${pid},'${app_name}',${server_port}, '${net_port:1}', '${Xmx}'); update tbl_application set run_status=1, ins_count=ins_count+1 where application_name='$app_name' and server_port='$server_port'; # Look here ! Look here ! EOF
    log "29"
  done
done