摘要：
备份MBR dd if=/dev/sda of=/opt/mbr.img bs=512 count=1 status=progress 恢复MBR dd if=/opt/mbr.img of=/dev/sdb status=progress 恢复bootloader dd if=/opt/mbr.i 阅读全文
摘要：
https://dev.mysql.com/doc/refman/8.0/en/miscellaneous-functions.html https://dev.mysql.com/doc/refman/8.0/en/built-in-function-reference.html left(str 阅读全文