What is the difference between empty and null in Salesforce?

Another one to test us on

From the outside the difference can appear very slight.  But to code that is running, it could mean very different outcomes!

In coding (once again I am assuming it is in the context of APEX), something could be NULL because it doesn't exist or hasn't been instanciated (ie it hasn't been created/setup).

Where as empty has two possible outcomes/possibilities.  It could mean that it is a string/text (as an empty) that is nothing.  For example ''.  There is nothing in between the ' and the '.  But the code has allocated memory to the variable, even if there isn't any actual text stored.  Additionally, it could also mean NULL (see above).

The Salesforce documentation also makes note of 'blank' which essentially has three possible outcomes: that whitespace is stored in the field, that '' is stored in the field, or NULL.  So when using forumals in Salesforce, I always try to use ISBLANK(), as it is the most 'inclusive' of the three functions.

IS Blank:

Its a function which validates whether the field has some value or not. Value can be some digit( 0-9), alphabet( a-z A-Z), special character ( %,$,--). If your  field contains any of them then this function will return  false. If it contains Blank (" ") or no value then it will return True.

IS NULL:

This function will consider Blank (" ") as some value. And if your field has Blank(" ") then it will return false considering 'Blank' also as some value.

For more information visit:

https://developer.salesforce.com/forums/?id=906F00000008nV0IAI