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* tblred: compute ("reduce") aggregations (e.g., sum, average) over groups defined by key columns.
* tbldesc: Summarize columns in file (e.g., proportion of character/numeric values, min/mean/median/max, missing values, correlation with a target column).
* tbljoin: Relational join without the need of pre-sorting and column matching.
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See HostedApps/MediaWiki for examples.