The LIBNAME Statement for Relational Databases

DBNULLKEYS= LIBNAME Option

Controls the format of the WHERE clause when you use the DBKEY= data set option.

Default value:	DBMS-specific
Valid in:	SAS/ACCESS LIBNAME statement
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= data set option, use DBNULLKEYS=YES. This is the default for most interfaces. When you specify DBNULLKEYS=YES and specify a column that is not defined as NOT NULL in the DBKEY= data set option, SAS generates a WHERE clause that can find NULL values. For example, if you specify DBKEY=COLUMN and COLUMN is not defined as NOT NULL, SAS generates a WHERE clause with the following 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. Note that 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 the DBKEY= option defines as NOT NULL, 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 that you specify in the DBKEY= option, then you can use DBNULLKEYS=NO. This is the default for the interface to Informix. If you specify DBNULLKEYS=NO and specify DBKEY=COLUMN, SAS generates a shorter form of the WHERE clause, regardless of whether the column specified in DBKEY= is defined as NOT NULL:

WHERE (COLUMN = ?)