=: equivalent to a = :b indicates that b is a bound variable, and variable binding is performed when execution is required : = is equivalent to assignment a in
general programming languages := 1 is to assign the number 1 to variable a
Or you can separate: and = to understand
In Oracle, : stands for reference, = stands for assignment
:= represents assignment
=: means that the value assigned is a reference value, that is, the value assigned is a variable, : can also be used alone to represent a reference to a variable