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i met a problem as the graph shows, thanks for helping me solve that question.

Looks like you are trying to change Field Type for a Standard field, which is not allowed by the system.
You can create a Custom Field as a work around

how can i create a custom field?

Ok, i got it.

Another question, how do i create a “select” type which can have month and year?


You can use the “Date” field instead. However, it will be shown in dd-mm-yyyy (or whatever format you have set in System Settings).

Hope this helps.

Thanks, but i can’t use date and system setting.