leftouter join

The leftouter join flavor returns all the records from the left side table and only matching records from the right side table.

Syntax

LeftTable | join kind=leftouter [ Hints ] RightTable on Conditions

Returns

Schema: All columns from both tables, including the matching keys.
Rows: All records from the left table and only matching rows from the right table.

Example

The result of a left outer join for tables X and Y always contains all records of the left table (X), even if the join condition doesn’t find any matching record in the right table (Y).

let X = datatable(Key:string, Value1:long)
[
    'a',1,
    'b',2,
    'b',3,
    'c',4
];
let Y = datatable(Key:string, Value2:long)
[
    'b',10,
    'c',20,
    'c',30,
    'd',40
];
X | join kind=leftouter Y on Key

Output

Related content

• Learn about other join flavors