Data Set Options for Relational Databases

DBNULLKEYS= Data Set Option

Controls the format of the WHERE clause with regard to NULL values when you use the DBKEY= data set option.

Default value:	LIBNAME setting
Valid in:	DATA and PROC steps (when accessing DBMS data using SAS/ACCESS software)
DBMS support:	Aster nCluster, DB2 under UNIX and PC Hosts, DB2 under z/OS, Greenplum, HP Neoview, Informix, Microsoft SQL Server, Netezza, ODBC, OLE DB, Oracle, Sybase IQ

Syntax
Details
See Also

Syntax

DBNULLKEYS=YES | NO

Details

If there might be NULL values in the transaction table or the master table for the columns that you specify in the DBKEY= option, then use DBNULLKEYS=YES. When you specify DBNULLKEYS=YES and specify a column that the DBKEY= data set option defines as NOT NULL, SAS generates a WHERE clause to find NULL values. For example, if you specify DBKEY=COLUMN and COLUMN is not defined as NOT NULL, SAS generates a WHERE clause with this syntax:

WHERE ((COLUMN = ?) OR ((COLUMN IS NULL) AND (? IS NULL)))

This syntax enables SAS to prepare the statement once and use it for any value (NULL or NOT NULL) in the column. This syntax has the potential to be much less efficient than the shorter form of the following WHERE clause. When you specify DBNULLKEYS=NO or specify a column that is defined as NOT NULL in the DBKEY= option, SAS generates a simple WHERE clause.

If you know that there are no NULL values in the transaction table or the master table for the columns you specify in the DBKEY= option, you can use DBNULLKEYS=NO. If you specify DBNULLKEYS=NO and specify DBKEY=COLUMN, SAS generates a shorter form of the WHERE clause, regardless of whether the column that is specified in DBKEY= is defined as NOT NULL:

WHERE (COLUMN = ?)