What is HL7?

Null, Empty and Invalid Values

Null (also referred to as Present But Null), Empty and Invalid values are important concepts in the HL7 world. They are defined as follows:

  • Null – A null value is sent to a receiving application when the sender wants to inform the receiver that it has no data for a specific field, subfield, or sub-subfield. Null is expressed using two double quotes. For example:|""|
  • Empty – An empty value is sent to a receiving application when the sender wants to inform the receiver that there is no explicit data for a specific field, subfield, or sub-subfield. Empty is expressed using no value. For example:||
  • Invalid – An invalid value is when incorrect data is inserted in a field, subfield, or sub-subfield. For example, when “XYZ” is inserted in a Date Time field:|XYZ|

The following table summarizes the results of using null, empty and invalid values with the 5.0 parser engine:

Data Type Data Type Result of Insert Result of Update
String <Empty> Not Inserted Not Updated
String “” NULL NULL
String <Not Empty> <Data> <Data>
Integer <Empty> or <Invalid> Not Inserted Not Updated
Integer “” NULL NULL
Integer <Not Empty> <Data> <Data>
Double <Empty> or <Invalid> Not Inserted Not Updated
Double “” NULL NULL
Double <Not Empty> <Data> <Data>
Date Time <Empty> or <Invalid> Not Inserted Not Updated
Date Time “” NULL NULL
Date Time <Not Empty> <Data> <Data

Note: If a key field is NULL or Present But Null and one or more columns are empty, an error will occur.

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