Data Model > Available DSCs > Relational MR database (RDB) CDSC > WHERE expressions supported natively
 
WHERE expressions supported natively
The Relational MR Database (RDB) CDSC supports some types of WHERE expression natively. That is, the CDSC includes the expression in the underlying SQL query that will be executed against the tables in the database schema. Native WHERE expressions can improve the performance of the RDB DSC 2, particularly when filtering data for tabulation (see IDataSet.Filter in the MDM Object Model Reference).
The WHERE expression types that are supported natively are shown in the following table. Support depends on the Relational MR Database CDSC schema (RDB DSC 2 or RDB DSC) in use in the connected data source:
Schema
Expression type
Examples
RDB DSC 2 or RDB DSC
Respondent.Serial system variable compared to a numeric value
Respondent.Serial >= 10000
Respondent.Serial < 2000
RDB DSC 2 only
Type
Logical (AND, OR)
=
< >
>
<
>=
<=
IS NULL
IS NOT NULL
mtLong
 
X
X
X
X
X
X
 
X
mtCategorical
 
 
 
 
 
X
 
 
X
Simple expression that is composed by a permitted expression
X
 
 
 
 
 
 
 
 
Note The variable that is being compared must be on the left-hand side of the comparison operator for both Long and Categorical comparisons. The variables must be in the HDATA top level, and mtCategorical only supports compare >=with {Single_Value}.
See also
Relational MR Database CDSC schema
Stored procedures
Upgrading older databases to the RDB DSC 2 schema
Known problems in Relational MR Database CDSC
Relational MR Database CDSC: Supported CDSC features
Relational MR database (RDB) CDSC