As-of joins are time-based joins - they join records from one table to another as-of a particular time or period of time. This is extremely useful functionality, particularly in the finance world - a common request, for example, is to find the prevailing quote in the market at the time a trade was placed. This becomes a straightforward task when using an as-of join.
The following joins fall under the general term 'as-of joins:'Â
Simple asof join (asof)