Not allow entering repeated references in a column - HOW?

  • Thread starter Thread starter ritinha
  • Start date Start date
R

ritinha

I have a table to register incoming documents. Its references ar
introduced in a column.
Each document must have a unique reference (e.g H04, H05, B01, B02
etc.).
Hence, repeated references must not occur.
What should I do to make sure that repeated references are no
introduced in the column... or alternatively, what should I do to mak
the system alert the user when he/she is introducing an existen
reference?

I look forward to receiving your help.
Thanks in advance,
Ritinh
 
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