union duplicate key

Start by running the reproduced UNION, JOIN, and inline-view SQL against the two matching MySQL tables and confirm the duplicated inline-view column alias k1 error. Trace the query-processing entry point that reports this error; done means the query executes without the reported duplicate-alias failure and existing behavior remains covered.

mysql table baseall and table test has the same tale struct and recored

show create table baseall;
+---------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+---------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| baseall | CREATE TABLE baseall (
k0 tinyint(1) DEFAULT NULL,
k1 tinyint DEFAULT NULL,
k2 smallint DEFAULT NULL,
k3 int DEFAULT NULL,
k4 bigint DEFAULT NULL,
k5 decimal(9,3) DEFAULT NULL,
k6 char(5) DEFAULT NULL,
k10 date DEFAULT NULL,
k11 datetime DEFAULT NULL,
k7 varchar(20) DEFAULT NULL,
k8 double DEFAULT NULL,
k9 float DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+---------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

show create table test;
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| test | CREATE TABLE test (
k0 tinyint(1) DEFAULT NULL,
k1 tinyint DEFAULT NULL,
k2 smallint DEFAULT NULL,
k3 int DEFAULT NULL,
k4 bigint DEFAULT NULL,
k5 decimal(9,3) DEFAULT NULL,
k6 char(5) DEFAULT NULL,
k10 date DEFAULT NULL,
k11 datetime DEFAULT NULL,
k7 varchar(20) DEFAULT NULL,
k8 double DEFAULT NULL,
k9 float DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

execute sql as follow:
SELECT *
FROM
(SELECT *
FROM
(SELECT k1, k2, k3, k4, k5, k6, k10, k11, k7, k8, k9
FROM test.baseall) AS t
LEFT JOIN
(SELECT k1, k2, k3, k4, k5, k6, k10, k11, k7, k8, k9
FROM test.test) AS t0
ON
t.k1 = t0.k1
UNION
SELECT *
FROM
(SELECT k1, k2, k3, k4, k5, k6, k10, k11, k7, k8, k9
FROM test.baseall) AS t1
RIGHT JOIN
(SELECT k1, k2, k3, k4, k5, k6, k10, k11, k7, k8, k9
FROM test.test) AS t2
ON
t1.k1 = t2.k1) AS t
LIMIT 1000

report error Duplicated inline view column alias k1 in inline view t