1. length:占用字节
    2. char_length:共有多个字符
    4. [root@localhost][(none)]: \s
    5. --------------
    6. mysql  Ver 14.14 Distrib 5.7.27, for linux-glibc2.12 (x86_64) using  EditLine wrapper
    8. Connection id:          11782
    9. Current database:
    10. Current user:           root@localhost
    11. SSL:                    Not in use
    12. Current pager:          stdout
    13. Using outfile:          ''
    14. Using delimiter:        ;
    15. Server version:         5.7.27-log MySQL Community Server (GPL)
    16. Protocol version:       10
    17. Connection:             Localhost via UNIX socket
    18. Server characterset:    utf8mb4
    19. Db     characterset:    utf8mb4
    20. Client characterset:    utf8mb4
    21. Conn.  characterset:    utf8mb4
    22. UNIX socket:            /mysql/tmp/mysql.sock
    23. Uptime:                 6 days 3 hours 38 min 4 sec
    25. Threads: 2  Questions: 183301  Slow queries: 173  Opens: 8061  Flush tables: 7  Open tables: 45  Queries per second avg: 0.344
    26. --------------
    28. [root@localhost][(none)]: select length('我'),char_length('我');
    29. +---------------+--------------------+
    30. | length('我')  | char_length('我')  |
    31. +---------------+--------------------+
    32. |             3 |                  1 |
    33. +---------------+--------------------+
    34. 1 row in set (0.00 sec)
    36. 转为16进制编码
    37. [root@localhost][(none)]: select hex('我');
    38. +------------+
    39. | hex('我')  |
    40. +------------+
    41. | E68891     |
    42. +------------+
    43. 1 row in set (0.00 sec)
    45. [root@localhost][(none)]: select 0xE68891;
    46. +----------+
    47. | 0xE68891 |
    48. +----------+
    49. | 我       |
    50. +----------+
    51. 1 row in set (0.00 sec)
    53. 不同字符集结果不一样
    54. [root@localhost][(none)]: set character_set_client=latin1;
    55. Query OK, 0 rows affected (0.00 sec)
    57. [root@localhost][(none)]: select length('我'),char_length('我');
    58. +-------------------+------------------------+
    59. | length('我')     | char_length('我')     |
    60. +-------------------+------------------------+
    61. |                 7 |                      3 |
    62. +-------------------+------------------------+
    63. 1 row in set (0.00 sec)
    65. [root@localhost][(none)]: select hex('我');
    66. +----------------+
    67. | hex('我')     |
    68. +----------------+
    69. | C3A6CB86E28098 |
    70. +----------------+
    71. 1 row in set (0.00 sec)