Question

Can someone explain to me what logic there is to enabling ANSI padding by default in SQL server.

Where the two code snippets below return true

if len('       ') = len('') begin
    print 'true'
end
else begin
    print 'false'
end

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

EDIT: I do not care about that you can turn it off. Does anyone know why it is on? Is it a database design decision? Is it a database optimisation? What are the positives of this being used? It certainly doesn’t make much sense to me – all I see are negatives.

Answer 1

To be compliant with the ANSI/ISO SQL-92 specification:

SQL Server follows the ANSI/ISO SQL-92 specification (Section 8.2,
, General rules #3) on how to compare strings
with spaces. The ANSI standard requires padding for the character
strings used in comparisons so that their lengths match before
comparing them. The padding directly affects the semantics of WHERE
and HAVING clause predicates and other Transact-SQL string
comparisons. For example, Transact-SQL considers the strings ‘abc’ and
‘abc ‘ to be equivalent for most comparison operations.