Domain check constraint

In summary, the domain check occurs first, then the trigger and finally the column constraint check. So, whenever a trigger is used to attempt to correct a value being inserted or updated, a domain check constraint should not be used. Instead a column check constraint should be used. 

An SQL domain is an extension of one of the built-in data types, but includes an optional check constraint. For example ... 

The SQL domain allows one to define which values are to be allowed in a particular column of a table. A domain is created by stating the underlying built-in SQL data type used to store the domain data type. In addition, a check constraint function may be used to allow or forbid certain values. This can be used to great advantage for SMILES and canonical SMILES. Using a domain improves the ability of the RDBMS to maintain the integrity of the data contained in its tables. 

The check constraint used in the creation of a domain is similar to the check constraint used in the creation of a table. For example, it would be possible to simply... 

Value Value matching utilizes domain constraints (e.g., drop lists, check boxes, and radio buttons). It becomes valuable when comparing two attributes that do not exactly match through their names. For example, consider attributes arrivalDate and checklnDay. These two attributes have associated value sets (Select), 1,2,..., 31 and (Day), 1,2,..., 31 respectively, and thus their content-based similarity is = 94%, which improves significantly over their term similarity (11(arr2 1Date)- = 18%). 

Three important and related technical points remain which are not standardized but central for tribological experiments they are related to the optical detection method used for most of the AFM. First, the laser beam must be centered on the cantilever end. The centring can easily be checked by scanning parallel and perpendicular to the cantilever symmetry axis. Secondly, for each apparatus, the four photodiodes quadrants orientation must be carefully checked (one method is described in fig lb). Lastly, one has to work within the linear response domain of the photodiodes, which implies a limited variation domain for the vertical movement of the sample when the vertical difference from the photodiodes signal is used. This constraint can be detoured by using horizontal difference signal, see ref (28,52). 

Besides the model management aspects, other types of knowledge support the engineer in the modeling task. For example, consistency checking of a design model can be performed in an automated fashion, if general rules or constraints of the domain are specified explicitly in a formal manner. 

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