TDengine -无效操作

Question

我试图执行sql：

select last(*) from mytable where index=index-1

描述mytable：

             Field              |         Type         |   Length    |   Note   |
=================================================================================
 ts                             | TIMESTAMP            |           8 |          |
 gauge                          | DOUBLE               |           8 |          |
 index                          | NCHAR                |          11 | TAG      |

结果发生错误：

Invalid operation

Answer 1

索引是nchar类型，因此您应该将SQL更改为

select last(*) from mytable where index='some_value';