Mount var to another directory, Mysql Database not found

I had an issue with rootfs and /dev/root/ because it was full at 100%. I did this command:

du -h

So I read this post:

How to increase the size of rootfs?

And I decided to mount /var to another directory by doing this:

mv /var /oldvar
mount --bind /home/vardisk /var 
cd /oldvar
tar cf - . |(cd /var; tar xpf -)

However, on my website, Mysql Database couldn’t be found. What can I do ? Thanks.