Guides
What is an AsOf Join?
Time series data is not always perfectly aligned.
Clocks may be slightly off, or there may be a delay between cause and effect.
This can make connecting two sets of ordered data challenging.
AsOf joins are a tool for solving this and other similar problems.  
One of the problems that AsOf joins are used to solve is
finding the value of a varying property at a specific point in time.
This use case is so common that it is where the name came from:  
_Give me the value of the property **as of this time**_.  
More generally, however, AsOf joins embody some common temporal analytic semantics,
which can be cumbersome and slow to implement in standard SQL.