Sorted:

Check if the date is within the specified range in Java.

Check if an index exists in MySQL.

Does MySQL include a string?

Inputting a character in C language to determine its type.

How to determine if a type in Python is NoneType?

Check if a field exists in mysql.

Is the Linux firewall disabled?

Check if Redis is running on Linux.

Check if a character array is empty in C language.

How to check if Windows is activated?