In ASE it is allowed to enclose strings in either double quotes or single quotes. In MS SQL Server, if SET QUOTED_IDENTIFIER is ON, only single quotes are allowed for string literals. Double quotes are used to introduce quoted identifiers when this setting is ON. If SET QUOTED_IDENTIFIER is OFF, both single and double quotes are allowed for string literals, but Intellisense does not recognize the version with double quotes. In the Isah database, QUOTED_IDENTIFIER is set to OFF.