Caché Transact-SQL (TSQL) Migration Guide - InterSystems ...

Caché TSQL Language ElementsThe following Caché ObjectScript example changes the empty string definition for the SAMPLES namespace. It first setsthe empty string value to a single blank space. It then sets the empty string value to the non-printing character representedby the ASCII code 0. (This example then immediately resets the empty string value to the Caché default):SET ^%SYS("sql","sys","namespace","SAMPLES","empty string")=" "WRITE !,"Empty string set to:"ZZDUMP ^%SYS("sql","sys","namespace","SAMPLES","empty string")SET ^%SYS("sql","sys","namespace","SAMPLES","empty string")=$CHAR(0)WRITE !,"Empty string set to:"ZZDUMP ^%SYS("sql","sys","namespace","SAMPLES","empty string")SET ^%SYS("sql","sys","namespace","SAMPLES","empty string")=""WRITE !,"Empty string reset to:"ZZDUMP ^%SYS("sql","sys","namespace","SAMPLES","empty string")WRITE !,!,"End of sample program"3.1.3 NULLIn TSQL a NULL supplied to a boolean operation returns as FALSE, as shown in the following example:DECLARE @var BINARY(1)SELECT @var=NULLIF @var PRINT "true" ELSE PRINT "false"In Sybase dialect, NULL is equal to NULL. A NULL=NULL comparison returns TRUE, and a NULL != NULL comparisonreturns FALSE.In MSSQL dialect, a comparison of NULL with any value returns FALSE. Thus NULL=NULL and NULL != NULLcomparisons both return FALSE.DECLARE @var BINARY(1)SELECT @var=NULLIF @var=NULL PRINT "true" ELSE PRINT "false"In Sybase dialect, NULL is not equal to any value. Therefore, Not Equals (!=) comparison involving NULL and any boolean,numeric, or string value (including the empty string ("")) returns TRUE. All Equals (=), Greater Than (>) or Less Than () or LessThan (