cycquery.ops.Join

class Join(join_table, on=None, on_to_type=None, cond=None, table_cols=None, join_table_cols=None, isouter=False)[source]

Bases: QueryOp

Join a table with another table.

Parameters:

  • join_table (Union[Select, Subquery, Table, DBTable]) – Table on which to join.

  • on (Union[str, List[str], Tuple[str], List[Tuple[str, str]], None]) – A list of strings or tuples representing columns on which to join. Strings represent columns of same name in both tables. A tuple of style (table_col, join_table_col) is used to join on columns of different names. Suggested to specify this parameter as opposed to cond.

  • on_to_type (Union[type, List[type], None]) – A list of types to which to convert the on columns before joining. Useful when two columns have the same values but in different format, e.g., strings of int.

  • cond (Optional[BinaryExpression]) – Condition on which to join to tables.

  • table_cols (Union[str, List[str], None]) – Filters to keep only these columns from the table.

  • join_table_cols (Union[str, List[str], None]) – Filters to keep only these columns from the join_table.

  • isouter (Optional[bool]) – Flag to say if the join is a left outer join.

Examples

>>> Join(table2, on=["col1", ("col2", "col3")], on_to_type=[int, str])(table1)
>>> Join(table2, table_cols=["col1", "col2"])(table1)
>>> Join(table2, join_table_cols=["col1", "col2"])(table1)

Warning

If neither on nor cond parameters are specified, an expensive Cartesian product is performed.

Methods

__call__(table)[source]

Process the table.

Parameters:

table (Union[Select, Subquery, Table, DBTable]) – Table on which to perform the operation.

Returns:

Processed table.

Return type:

sqlalchemy.sql.selectable.Subquery