Question

Unlike programming languages, SQL doesn’t allow variable to be assigned a value using the following syntax ( instead we must use SET or SELECT ):

@i=100; //error

Is there particular reason why SQL doesn’t allow this?

thank you

Answer 1

The first reason that comes to mind is that SQL uses the ‘=’-sign for both comparing of values as setting of values. This means that it requires a different syntax to distinguish between comparing and setting of the values. In (some) other programming there is a distinction between setting and comparing the values with the use of the ‘=’-sign and the ‘==’-sign.
For example in SQL:

SET @a = 100 --To set the value of @a.
if (@a = 100) -- To compare the value of @a.

For example in C#:

a = 100; //To set the value of a.
if (a == 100) //To compare the value of a.