join

Operator

  join — combine data from two inputs using a join predicate

Synopsis

( => left path => right path )
| [anti|inner|left|right] join on <left-key>=<right-key> [<field>:=<right-expr>, ...]

Description

The join operator combines records from two inputs based on whether the <left-key> expression (evaluated in the context of the left input) is equal to the <right-key> expression (evaluated in the context of the right input) omitting values where there is no match (or including them in the case of anti join).

The available join types are:

• inner - output only values that match
• left - output all left values with merged components from <right-expr>
• right - output as a left join but with the roles of the inputs and <right-expr> reversed
• anti - output left values whose left key does not have a matching right key

For anti join, the <right-expr> is undefined and thus cannot be specified.

Currently, only exact equi-join is supported and the inputs must be sorted in ascending order by their respective keys. Also, the join keys must be field expressions. A future version of join will not require sorted inputs and will have more flexible join expressions.

Examples

The join tutorial includes several examples.