SAS/ACCESS 9.2 for Relational Databases: Reference, Fourth Edition

The LIBNAME Statement for Relational Databases 4 DBNULLKEYS= LIBNAME Option 133DBNULLKEYS= LIBNAME OptionControls the format of the WHERE clause when you use the DBKEY= data set option.Default value:Valid in:DBMS-specificSAS/ACCESS LIBNAME statementDBMS 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 IQSyntaxDBNULLKEYS=YES | NODetailsIf there might be NULL values in the transaction table or the master table for thecolumns that you specify in the DBKEY= data set option, use DBNULLKEYS=YES.This is the default for most interfaces. When you specify DBNULLKEYS=YES andspecify 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 youspecify DBKEY=COLUMN and COLUMN is not defined as NOT NULL, SAS generatesa 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 bemuch less efficient than the shorter form of the following WHERE clause. When youspecify DBNULLKEYS=NO or specify a column that the DBKEY= option defines asNOT NULL, SAS generates a simple WHERE clause.If you know that there are no NULL values in the transaction table or the mastertable for the columns that you specify in the DBKEY= option, then you can useDBNULLKEYS=NO. This is the default for the interface to Informix. If you specifyDBNULLKEYS=NO and specify DBKEY=COLUMN, SAS generates a shorter form ofthe WHERE clause, regardless of whether the column specified in DBKEY= is definedas NOT NULL:WHERE (COLUMN = ?)See AlsoTo apply this option to an individual data set, see the “DBNULLKEYS= Data SetOption” on page 311.“DBKEY= Data Set Option” on page 305