On Wed, 30 Jul 2014, Michael Bayer wrote:
Typically a UNIQUE constraint is placed on the "natural" key to prevent
dupes.
I can see this when the natural key is a single column, but wonder how a
compound natural key is represented if a serial integer is used as the
surrogate 'id' key. For example,
class Changed_Data(Base):
__tablename__ = changed_data
id = Column(Integer, primary_key = True)
which_table = Column(unicode(32), nullable = False)
which_attrib = Column(unicode(32), nullable = False)
when_changed = Column(Timestamp, nullable = False)
curr_value = Column(Unicode(32), nullable = False)
new_value = Column(Unicode(32), nullable = False)
changed_by = Column(Unicode(32), nullable = False)
reason = Column(Text)
The postgres schema specifies the primary key as (which_table,
which_attribute, when_changed). If I make each of those columns Unique is it
the set of columns that is unique or each individual column?
TIA,
Rich
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