MySQL 5.7.12 Command Line Clientでユーザーを追加しても切り替えられないので、Stackoverflowで調べたら、ようやく分かりました。
I couldn’t switch the user even though I’ve added on MySQL 5.7.12 Command Line Client, but I’ve found out watching Stackoverflow.

By the way, I’ve cut that command in there.

With entering the command on “THE NORMAL COMMAND PROMPT”, I could switch.

> mysql -u 12345USERNAME12345 -h localhost -p 12345PASSWORD12345

※-h localhostが抜けていると、何故か使えませんでした。
*** without “-h localhost”, I couldn’t connect somehow.

* replace 12345USERNAME12345 to the login username (like root)

* replace 12345PASSWORD12345 to password


To be sure, we have to move to the directory which the mysql.exe has without having mysql.exe on the “Path”.

By the way, this information didn’t come up with Japanese Searching.