"Purge" vs. "expunge"

Solution 1:

I think the basic denotative (surface) meaning would be understood to be the same. In both cases, the duplicate records were removed. The connotation is different, I think—at least to some people. I'll use the Oxford English Dictionary's definitions to explain why I think that.

Expunge has the following etymology:

Latin expungĕre to mark for deletion (a name in a list) by points set above or below, < ex out + pungĕre to prick.

Three definitions are given, all minor variations on the same theme:

To strike out, blot out, erase, omit (a name or word from a list, a phrase or passage from a book or record).

It's a very straightforward word, and it fits perfectly in your example sentence.

Purge has a more complicated history. The following is excerpted from the etymology section of the OED's entry for the word; I've broken it into bullet points for ease of reading and removed some meanings that are very similar to each other or irrelevant to this discussion:

Anglo-Norman purgir, porger, pourger, Anglo-Norman and Old French, Middle French purgier, Anglo-Norman and Old French, Middle French, French purger

• to purify (the soul) (end of the 12th cent.)
• to free (an object) from impurities (c1200, earliest with reference to threshing corn)
• to rid (the body) from impurities (c1265 in a medical context; 14th cent. used reflexively)
• to rid (an organization or party) of people regarded as undesirable (1789)

variant (with elision of medial -i-) of early Latin pūrigāre < pūrus pure adj.+ -igāre, verbal suffix also seen in lītigāre litigate v.

The point is that although purge can be used in the way you suggest in your example, it carries the connotation of purification, of removal of sin or waste matter (i.e. feces or vomit) or something harmful. This isn't ancient linguistic history—this definition of purge is common and current:

To rid one's body of waste or harmful material; spec. to vomit or to empty one's bowels (esp. by taking a laxative).

The definition that's closest to your example is:

To make physically pure or clean by the removal of dirt, impurities, or waste matter; to rid or free of or (rare) from impurities or imperfections.

Note that it calls your grammatical structure, "records were purged from the book," rare, though it doesn't seem unusual to me.

Because of the associations this word carries, to me it feels stronger. I'd expunge duplicate records from a book. I'd purge my totalitarian regime of dissidents.

Solution 2:

In the case of your two example sentences, their meaning is basically the same. The two words expunge and purge have similar and sometimes overlapping meanings, however they generally have different primary purposes.

The word purge is generally used when cleaning or to indicate purification, removal of unnecessary or useless quantities. The end result of purging is a purer essence of the remainder.

The word expunge is simpler, and has a more straightforward meaning. It generally, and simply, means to obliterate, to wipe out completely, leaving no trace behind. There is no connotation of the quality of what remains, simply the completeness of the elimination of what was removed.