Query result is not compatible with MySQL while using in clause for enum type

[PragmaTwice]

Bug Report

(Maybe a MySQL issue)

1. Minimal reproduce step (Required)

create table a(b datetime, c enum('David'), d double);
replace a set b = '2030-05-19', c = 'David', d = 0;
SELECT d FROM a WHERE c IN(SELECT d WHERE b);

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

in MySQL:

+------+
| d    |
+------+
|    0 |
+------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

Empty set (0.01 sec)

4. What is your TiDB version? (Required)

+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()

                                                                            |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.2.0-alpha-316-g014005ab6
Edition: Community
Git Commit Hash: 014005ab68b5c9a28795d13c1ca685cf46a3be7e
Git Branch: master
UTC Build Time: 2021-07-17 09:44:18
GoVersion: go1.16.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[dveeden]

SELECT c IN(SELECT d WHERE b) FROM a also shows the difference.

[guo-shaoge]

Behavior of MySQL is inconsistent. IMO, it's a MySQL's bug(bug report)

drop table if exists t1;
create table t1(col_datetime datetime, col_enum enum('ABC'), col_double double);
insert into t1 values('2030-05-19', 'ABC', 0);                                                                                                                                                                                                                                
select 1 from t1 where col_enum IN (select col_double where col_datetime);
select 1 from t1 where col_enum IN (select col_double);

mysql> select 1 from t1 where col_enum IN (select col_double where col_datetime);
+---+
| 1 |
+---+
| 1 |
+---+
1 row in set (0.00 sec)

mysql> select 1 from t1 where col_enum IN (select col_double);
Empty set (0.00 sec)

TiDB's result is reasonable. I will make this issue as compatiblility issue after bug report is verified.

[XuHuaiyu]

Verified in MySQL:

Actually, this is a bug, but with a very low priority.

[ti-srebot]

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