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SubString( character_expression, start, length )
Returns the part of character_expression starting at the position start for length characters.
Example
select SubString( 'abcde', 3, 2 )
Differences
If ‘start’ ≤ 0 or if ‘start’ is larger than the length of character_expression, ASE returns NULL. Remember that in ASE the NULL string is treated as the empty string in MS SQL Server. In MS SQL Server, if the ‘start’ ≤ 0, the length of the resulting string is smaller than ‘length’. All positions up to position 1 count as an empty string.
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ASE |
MS SQL Server |
SubString( 'abcde', 2, 3 ) |
'bcd' |
'bcd' |
SubString( 'abcde', 1, 3 ) |
'abc' |
'abc' |
SubString( 'abcde', 0, 3 ) |
NULL |
'ab' |
SubString( 'abcde', −1, 3 ) |
NULL |
'a' |
If ‘start’ is larger than the length of character_expression, MS SQL Server returns the empty string, whereas ASE returns the NULL string. Remember, however, that the NULL string in ASE behaves like the empty string.
Finally, if ‘character_expression’ equals NULL, ASE returns NULL, whereas MS SQL Server returns an error message.