UD Update Code

(a limit field)

20001031 in ud

ud=20001001-20001031

The UD field contains the date, in YYYYMMDD format, a record was entered into the NLM system as an in-process record, a completed record, or a revised record. NLM has enhanced date information available for this edition of the database, therefore, this field includes any record activity. In previous editions, the UD field indicated only the date NLM entered the record into MEDLINE as a completed record.

All records in the MEDLINE database contain an entry date and a completion date in addition to an update code. The entry date, displayed in the Entry Date (DA) field, indicates when the record was entered into the NLM system as an in-process record; the completion date, displayed in the Completion Date (CD) field, indicates when NLM assigned fully-indexed status to the record. Any record with revisions, such as corrections or new indexing, also contains a revision date, displayed in the Revision Date (DR) field.

Retrieving Newly-Added MEDLINE Records

Use the Completion Date (CD) field to retrieve records added most recently to the MEDLINE database. NLM assigns a completion date to fully-indexed records only. The search 20010301 in cd retrieves fully-indexed records added to MEDLINE on March 1, 2001. Note that in previous editions of MEDLINE, the UD field indicated only the date NLM entered the record into MEDLINE as a completed record.

Retrieving Revised Records

Use the Revision Date (DR) field to retrieve MEDLINE records that have had corrections, new data, or new indexing. The search 20010301 in dr retrieves only records revised on March 1, 2001.

You can search for an individual code or a range of codes in this field.

Browsing Update Codes

As an alternative to searching with the field label, you can browse codes and search for them directly from the Update Code Field-Specific Index. This field-specific index contains only update codes used in the database. Results of a search in this index display in the UD field.