What Is ID In Apex?
Any valid ID (18-character Salesforce Platform identifier). If you set ID to a 15-character value then apex converts its value to its 18-character representation.
Id recordId = '0012w00001UNkDQAA1';
Note:All invalid ID values are rejected with a runtime exception.
What Is Blob In Apex?
A collection of binary data stored as a single object.
A blob is typically used to store images, audio, or other multimedia objects, and sometimes binary executable code is also stored as a blob. We can convert this datatype to string or from string using the toString() and valueOf() methods.
Syntax Of Blob Data Type
String s = ‘abc’; Blob b = Blob.valueOf(s); String s1 = b.toString();