Delete Similar Records

To delete similar records, i.e. where the records are not the same but one field is the same and only one copy needs to be preserved, try the following SQL:

delete from T1
from MyTable T1, MyTable T2
where T1.dupField = T2.dupField
and T1.uniqueField > T2.uniqueField

This will delete all records from the table MyTable which have the same value for the field dupField, leaving that record which has the lowest value in uniqueField.