举一个简单的例子，其中一列数据需要用 SQL 中的枚举类型表示：
+------------------------------------------+
| user |
+----+------+-----+------------------------+
| id | name | age | relationship_status_id |
+----+------+-----+------------------------+
| 1 | John | 27 | 3 |
| 2 | Mary | 77 | 1 |
| 3 | Jack | 40 | 4 |
+----+------+-----+------------------------+
+---------------------+
| relationship_status |
+----+----------------+
| id | name |
+----+----------------+
| 1 | married |
| 2 | widowed |
| 3 | single |
| 4 | divorced |
+----+----------------+
在 …