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

778 Sybase IQ Null Values 4 Chapter 27Sybase IQ Null ValuesSybase IQ has a special value called NULL. A Sybase IQ NULL value means anabsence of information and is analogous to a SAS missing value. When SAS/ACCESSreads a Sybase IQ NULL value, it interprets it as a SAS missing value.You can define a column in a Sybase IQ table so that it requires data. To do this inSQL, you specify a column as NOT NULL, which tells SQL to allow only a row to beadded to a table if a value exists for the field. For example, NOT NULL assigned to theCUSTOMER field in the SASDEMO.CUSTOMER table does not allow a row to beadded unless there is a value for CUSTOMER. When creating a table withSAS/ACCESS, you can use the DBNULL= data set option to indicate whether NULL isa valid value for specified columns.You can also define Sybase IQ columns as NOT NULL DEFAULT. For moreinformation about using the NOT NULL DEFAULT value, see your Sybase IQ ReferenceManual.Knowing whether a Sybase IQ column allows NULLs or whether the host systemsupplies a default value for a column that is defined as NOT NULL DEFAULT can helpyou write selection criteria and enter values to update a table. Unless a column isdefined as NOT NULL or NOT NULL DEFAULT, it allows NULL values.For more information about how SAS handles NULL values, see “Potential ResultSet Differences When Processing Null Data” on page 31.To control how the DBMS handles SAS missing character values, use theNULLCHAR= and NULLCHARVAL= data set options.LIBNAME Statement Data ConversionsThis table shows the default formats that SAS/ACCESS Interface to Sybase IQassigns to SAS variables to read from a Sybase IQ table when using the “Overview ofthe LIBNAME Statement for Relational Databases” on page 87. These default formatsare based on Sybase IQ column attributes.Table 27.4LIBNAME Statement: Default SAS Formats for Sybase IQ Data TypesSybase IQ Data Type SAS Data Type Default SAS FormatCHAR(n)* character $n.VARCHAR(n)* character $n.LONG VARCHAR(n)* character $n.BIGINT numeric 20.SMALLINTTINYINTnumericnumeric6.4.INTEGER numeric 11.BIT numeric 1.DOUBLE numeric noneREAL numeric noneFLOAT numeric noneDECIMAL(p,s) numeric m.nNUMERIC(p,s) numeric m.n