DataFrame.join

DataFrame join(DataFrame other,  string on,
          JoinKind kind =  JoinKind.INNER,  string suffix =  "_right")

Joins another frame on equal-dtype key columns (INNER default, or LEFT): rows in left-frame order, right-frame order within one left row; null keys never match; the key coalesces; right-side collisions get the suffix.

Parameters

`other`	the right frame
`on`	the key column name, present in both frames
`kind`	INNER or LEFT
`suffix`	the right-side collision suffix

Returns

the joined frame.

Throws

DataFrameException for missing columns or differing key

dtypes.

DataFrame join(DataFrame other,  string[]  leftOn,  string[]  rightOn,
          JoinKind kind =  JoinKind.INNER,  string suffix =  "_right")

Ditto, the multi-column join (ADR-2026-10-30-03): a row matches only when every key pair holds; any null component never matches. OUTER coalesces every paired key column.

Parameters

`other`	the right frame
`leftOn`	the left key column names
`rightOn`	the right key column names (same length)
`kind`	the join kind
`suffix`	the right-side collision suffix

Returns

the joined frame.

Throws

DataFrameException on missing columns, length

mismatches, empty keys or per-pair dtype/kind violations.

DataFrame join(DataFrame other,  string[]  on,
          JoinKind kind =  JoinKind.INNER,  string suffix =  "_right")

Ditto, the same key names on both sides.

DataFrame join(DataFrame other,  string leftOn,  string rightOn,
          JoinKind kind =  JoinKind.INNER,  string suffix =  "_right")

Ditto, with different key column names on the two sides.

Parameters

`other`	the right frame
`leftOn`	the left key column name
`rightOn`	the right key column name
`kind`	INNER or LEFT
`suffix`	the right-side collision suffix

Returns

the joined frame.