Contributor
Posts: 53

# What is the difference between if a and if a and not b

Hi,

Please can someone explain with a simple dataset merge and proc sql example the difference between following scenarios:

1. if a

2. if b

3. if a and not b

4. if not a and b

Thanks

Super User
Posts: 23,693

Super User
Posts: 6,759

## Re: What is the difference between if a and if a and not b

These are simple logical conditions, whether it's a DATA step, SQL, or a treatise by Aristotle.

Assuming that "a" and "b" can be either true or false:

if a ==> true whenever "a" is true, regardless of the value of "b"

if b ==> true whenever "b" is true, regardless of the value of "a"

if a and not b ==> true whenever "a" is true and "b" is false

if not a and b ==> true whenever "a" is false and "b" is true

In SAS programming, if "a" and "b" represent numeric amounts rather than comparisons, SAS considers 0 and missing to be false and any other value to be true.

Good luck.

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