ANSI_NULLS and QUOTED_IDENTIFIER killed things. What are they for?

Question

NOTE: I checked Understanding QUOTED_IDENTIFIER and it does not answer my question.

I got my DBAs to run an index I made on my Prod servers (they looked it over and

Answer 1

ANSI_NULLS ON makes any binary boolean expression with a null value evaluate to false. Using the following template:

declare @varA, @varB int

if 
begin
    print 'true'
end
else
begin
    print 'false'
end


@varA: NULL; @varB: NULL; @varA = @varB evaluates to false
@varA: 1; @varB: NULL; @varA <> @varB evaluates to false

The proper way to test for null is to use is [not] NULL

@varA: NULL; @varA is NULL evaluates to true
@varA: 1; @varA is not NULL evaluates to true

QUOTED_IDENTIFER ON merely allows you to use double quotes to delimit identifiers (bad idea IMO, just user square brackets)

from tblA "a" -- ok when ON, not ok when OFF
from tblA [a] -- always ok