Excel check if value already exists

Describes the cause and action for error messages.

Error Message(English)：
check if value already exists

Resolution

How to check if value already exists? - Stack Overflow
https://stackoverflow.com/questions/34239345/how-to-check-if-value-already-exists

php - check if value already exists in MySQL | DaniWeb
https://www.daniweb.com/programming/web-development/threads/442565/check-if-value-already-exists-in-・・・

Unique Array Values in JavaScript, performance rundown for Node.js ...
https://medium.com/@jakubsynowiec/unique-array-values-in-javascript-7c932682766c