This example shows an instance of the DataSubset specialization of the WhereClause class that defines a compound expression for "Example flag 1 is not missing or N". The compound expression of the DataSubset class negates :
- Negates another compound expression that specifies that the value of the EXMPFL variable in the ADVS dataset is missing or the value of the EXMPFL variable in the ADVS dataset is equal to "N".
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- Could be expressed as:
NOT (ADVS.EXMPLFL EQ '' OR ADVS.EXMPLFL EQ 'N')
Note that this is a relatively simple example that has been created to illustrate the use of "NOT"; in practice, it would be better to simplify this criterion by using the logically equivalent inverse criterion: ADVS.EXMPLFL NE '' AND ADVS.EXMPLFL NE 'N'. The "NOT" logical operator would generally be used to negate more complex compound expressions where the logically inverse criterion is more difficult to express.
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