select big_unsigned_int union decimal differ from mysql

[XuHuaiyu]

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db.txt

result of TiDB

tidb>  select `col_bigint_unsigned_key` from table90_int_autoinc union select  `col_decimal_10_4_signed_key` from `table90_int_autoinc` order by col_bigint_unsigned_key;
+-------------------------+
| col_bigint_unsigned_key |
+-------------------------+
|                    NULL |
|                  0.0000 |
|                  0.1123 |
|                  1.0000 |
|                  1.0090 |
|                  1.0988 |
|                 12.9873 |
|                 12.9910 |
|                 13.0000 |
|                 27.0000 |
|                 74.0000 |
|                 82.0000 |
|                 90.0000 |
|                 93.0000 |
|                981.0000 |
|               1235.0000 |
|               2909.0000 |
|              13982.0000 |
|              32259.0000 |
+-------------------------+
19 rows in set (0.00 sec)

result of MySQL:

mysql> select `col_bigint_unsigned_key` from table90_int_autoinc union select  `col_decimal_10_4_signed_key` from `table90_int_autoinc` order by col_bigint_unsigned_key;
+-------------------------+
| col_bigint_unsigned_key |
+-------------------------+
|                    NULL |
|             -27110.0000 |
|             -20764.0000 |
|               -111.1212 |
|                -83.0000 |
|                 -9.1823 |
|                 -1.0000 |
|                 -0.9871 |
|                  0.0000 |
|                  0.1123 |
|                  1.0000 |
|                  1.0090 |
|                  1.0988 |
|                 12.9873 |
|                 12.9910 |
|                 13.0000 |
|                 27.0000 |
|                 74.0000 |
|                 82.0000 |
|                 90.0000 |
|                 93.0000 |
|                981.0000 |
|               1235.0000 |
|               2909.0000 |
|              13982.0000 |
|              32259.0000 |
+-------------------------+
26 rows in set (0.00 sec)

tidb_version:
tidb> select tidb_version();

+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                       |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v2.1.0-beta-133-gd2aab148
Git Commit Hash: d2aab148fccb792b40f824f603dea3e7ba245d67
Git Branch: master
UTC Build Time: 2018-07-31 03:15:42
GoVersion: go version go1.10.3 darwin/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e |
+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[XuHuaiyu]

@lysu PTAL