Not unique table/alias runs normally

[xiongjiwei]

Bug Report

Please answer these questions before submitting your issue. Thanks!

same with #24563

1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

use test;
create table t(a int);
mysql> select 2 from test.t, t;
ERROR 1066 (42000): Not unique table/alias: 't'

3. What did you see instead (Required)

use test;
create table t(a int);
mysql> select 2 from test.t, t;
Empty set (0.01 sec)

4. What is your TiDB version? (Required)