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

Data Set Options for Relational Databases 4 DBKEY= Data Set Option 305DBKEY= Data Set OptionSpecifies a key column to optimize DBMS retrieval.Default value:noneValid in: DATA and PROC steps (when accessing DBMS data using SAS/ACCESSsoftware)DBMS support: Aster nCluster, DB2 under UNIX and PC Hosts, DB2 under z/OS,Greenplum, HP Neoview, Informix, Microsoft SQL Server, MySQL, Netezza, ODBC,OLE DB, Oracle, Sybase, Sybase IQ, TeradataSyntaxDBKEY=(column-1)Syntax DescriptioncolumnSAS uses this to build an internal WHERE clause to search for matches in theDBMS table based on the key column. For example:select * from sas.a, dbms.b(dbkey=x) where a.x=b.x;In this example, DBKEY= specifies column x, which matches the key column thatthe WHERE clause designates. However, if the DBKEY= column does NOT matchthe key column in the WHERE clause, DBKEY= is not used.DetailsYou can use this option to potentially improve performance when you are processing ajoin that involves a large DBMS table and a small SAS data set or DBMS table.When you specify DBKEY=, it is strongly recommended that an index exists for thekey column in the underlying DBMS table. Performance can be severely degradedwithout an index.CAUTION:Improper use of this option can decrease performance. For detailed informationabout using this option, see the “Using the DBINDEX=, DBKEY=, andMULTI_DATASRC_OPT= Options” on page 48. 4ExamplesThis example uses DBKEY= with the MODIFY statement in a DATA step:libname invty db2;data invty.stock;set addinv;modify invty.stock(dbkey=partno) key=dbkey;INSTOCK=instock+nwstock;RECDATE=today();if _iorc_=0 then replace;