通过嵌套循环实现 

#! /bin/bash

back_user="-uroot -pRoot=12345."
back_dir=/backup/one
#获取数据库名
mysql ${back_user} -N -e 'show databases' | grep -Ev 'sys|mysql|information_schema|performance_schema' > dbs

while read dbname
do
  [ -d ${back_dir}/$dbname ] || mkdir -p ${back_dir}/$dbname
  #库备份
  mysqldump ${back_user} $dbname | gzip > ${back_dir}/$dbname/"$dbname"_$(date +%F).sql.gz
  #获取数据库中表名
  mysql ${back_user} -N -e "show tables from $dbname" > tbs
  while read tbname
  do
  #表备份
  mysqldump ${back_user} $dbname | gzip > ${back_dir}/$dbname/"$dbname"-"$tbname"_$(date +%F).sql.gz
  done < tbs
done < dbs

rm -rf  dbs tbs

 后续进行删除数据库中的部分数据检测是否备份成功