写一个脚本zl.sh，用来删除数据库mydatabase中某个表mytable的某行数据：

#!/bin/bash
HOSTNAME="127.0.0.1"
PORT="2918"
USERNAME="root"
PASSWORD="root"

TABLENAME="mydatabase"
DATABASEUSERDB="mytable"

MYSQL_CMD="mysql -h${HOSTNAME}  -P${PORT}  -u${USERNAME} -p${PASSWORD}"

alter_table_sql = "delete from ${TABLENAME} where id = '123'"
echo ${alter_table_sql} | ${MYSQL_CMD} ${DATABASEUSERDB}

执行脚本：sh zl.sh

报错：alter_table_sql:not found

解决方法：

alter_table_sql和等号之间不要有空格：

alter_table_sql="delete from ${TABLENAME} where id = '123'"