the column name return from join is ambiguous

[jjtjiang]

`the column name return from join is ambiguous ,sometimes it return the table.column_name and sometimes it return the column_name rather than table.column_name;

CREATE TABLE test.a
(
id Int8,
name String
)
ENGINE = Memory

insert into a values (1,'name') ;

SELECT *
FROM
(
SELECT *
FROM a
) AS a1
INNER JOIN
(
SELECT *
FROM a
) AS a2 ON a1.id = a2.id
┌─id─┬─name─┬─a2.id─┬─a2.name─┐
│ 1 │ name │ 1 │ name │
└────┴──────┴───────┴─────────┘

this case return column_name;

SELECT *
FROM
(
SELECT *
FROM a
) AS a1
INNER JOIN
(
SELECT *
FROM a
) AS a2 ON a1.id = a2.id
INNER JOIN
(
SELECT *
FROM a
) AS a3 ON a2.id = a3.id

┌─a1.id─┬─a1.name─┬─a2.id─┬─a2.name─┬─a3.id─┬─a3.name─┐
│ 1 │ name │ 1 │ name │ 1 │ name │
└───────┴─────────┴───────┴─────────┴───────┴─────────┘

this case return table.column_name;`