Method test_union_correspondence

test/sql/test_selectable.py:977–1027

(self)

        )

    def test_union_correspondence(self):
        # tests that we can correspond a column in a Select statement
        # with a certain Table, against a column in a Union where one of
        # its underlying Selects matches to that same Table

        u = select(
            table1.c.col1,
            table1.c.col2,
            table1.c.col3,
            table1.c.colx,
            null().label("coly"),
        ).union(
            select(
                table2.c.col1,
                table2.c.col2,
                table2.c.col3,
                null().label("colx"),
                table2.c.coly,
            )
        )
        s1 = table1.select().set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)
        s2 = table2.select().set_label_style(LABEL_STYLE_TABLENAME_PLUS_COL)

        assert (
            u.corresponding_column(s1.selected_columns.table1_col2)
            is u.selected_columns.col2
        )

        # right now, the "selected_columns" of a union are those of the
        # first selectable.  so without using a subquery that represents
        # all the SELECTs in the union, we can't do corresponding column
        # like this.  perhaps compoundselect shouldn't even implement
        # .corresponding_column directly
        assert (
            u.corresponding_column(s2.selected_columns.table2_col2) is None
        )  # really? u.selected_columns.col2

        usub = u.subquery()
        assert (
            usub.corresponding_column(s1.selected_columns.table1_col2)
            is usub.c.col2
        )
        assert (
            usub.corresponding_column(s2.selected_columns.table2_col2)
            is usub.c.col2
        )

        s1sub = s1.subquery()
        s2sub = s2.subquery()
        assert usub.corresponding_column(s1sub.c.table1_col2) is usub.c.col2
        assert usub.corresponding_column(s2sub.c.table2_col2) is usub.c.col2

    def test_union_precedence(self):
        # conflicting column correspondence should be resolved based on