Joins

uj (union-join): returns a table with combined rows and columns of both tables.

lj (left-join): returns a table with all rows from left table and the first matching row from the right table leaving non-matching rows as none.

ij (inner-join): returns a table with rows from both tables when there is a match.

aj (asof-join): returns a table with rows from both tables matched on equality and most-recent values.