Indeed, Sybase for instance treats a single space (e.g. ' ') the same as an empty string (e.g. ''). For the purpose of concatenating in Sybase, NULL is '' (and

Indeed, Sybase for instance treats a single space (e.g. ' ') the same as an empty string (e.g. ''). For the purpose of concatenating in Sybase, NULL is '' (and thus ' '). So `SELECT a = "a" + NULL` would yield a = "a". But so would `SELECT a = "a" + " "`. MSSQL allows this behaviour, since it's based on Sybase, but you have to explicitly turn it on.