feat(query): add collation

[sundy-li]

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Summary

Summary about this PR

Fixes #8104

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1 Ignored Deployment

Name	Status	Preview	Updated
databend	⬜️ Ignored (Inspect)		Nov 3, 2022 at 0:40AM (UTC)

[sundy-li]

MySQL [(none)]> select substr('城区-主城区-其他', 1, 6), length('我爱中国');
+---------------------------------------------------+------------------------+
| substring('城区-主城区-其他' from 1 for 6)        | length('我爱中国')     |
+---------------------------------------------------+------------------------+
| 城区                                              |                     12 |
+---------------------------------------------------+------------------------+
1 row in set (0.030 sec)

MySQL [(none)]> set collation = 'utf8';
Query OK, 0 rows affected (0.028 sec)

MySQL [(none)]> select substr('城区-主城区-其他', 1, 6), length('我爱中国');
+---------------------------------------------------+------------------------+
| substring('城区-主城区-其他' from 1 for 6)        | length('我爱中国')     |
+---------------------------------------------------+------------------------+
| 城区-主城区                                       |                      4 |
+---------------------------------------------------+------------------------+
1 row in set (0.036 sec)

[BohuTANG]

CI checking failure :)

[FANNG1]

why “binary” is the default value not utf-8？

[sundy-li]

Because the string column is stored as binary by default.

[sundy-li]

You can set global to make it default to use utf8