# HetuEngine预留关键字
[表1]罗列了系统预留的关键字，以及它们在其他SQL标准中是否为预留关键字。如果需要使用这些关键字作为标识符，请加注双引号。
 表1关键字 
| Keyword           | SQL：2016 | SQL-92   |
|:---|:---|:---|
| ALTER             | reserved | reserved |
| AND               | reserved | reserved |
| AS                | reserved | reserved |
| BETWEEN           | reserved | reserved |
| BY                | reserved | reserved |
| CASE              | reserved | reserved |
| CAST              | reserved | reserved |
| CONSTRAINT        | reserved | reserved |
| CREATE            | reserved | reserved |
| CROSS             | reserved | reserved |
| CUBE              | reserved | reserved |
| CURRENT_DATE      | reserved | reserved |
| CURRENT_PATH      | reserved | reserved |
| CURRENT_ROLE      | reserved | reserved |
| CURRENT_TIME      | reserved | reserved |
| CURRENT_TIMESTAMP | reserved | reserved |
| CURRENT_USER      | reserved | reserved |
| DEALLOCATE        | reserved | reserved |
| DELETE            | reserved | reserved |
| DESCRIBE          | reserved | reserved |
| DISTINCT          | reserved | reserved |
| DROP              | reserved | reserved |
| ELSE              | reserved | reserved |
| END               | reserved | reserved |
| ESCAPE            | reserved | reserved |
| EXCEPT            | reserved | reserved |
| EXECUTE           | reserved | reserved |
| EXISTS            | reserved | reserved |
| EXTRACT           | reserved | reserved |
| FALSE             | reserved | reserved |
| FOR               | reserved | reserved |
| FROM              | reserved | reserved |
| FULL              | reserved | reserved |
| GROUP             | reserved | reserved |
| GROUPING          | reserved | reserved |
| HAVING            | reserved | reserved |
| IN                | reserved | reserved |
| INNER             | reserved | reserved |
| INSERT            | reserved | reserved |
| INTERSECT         | reserved | reserved |
| INTO              | reserved | reserved |
| IS                | reserved | reserved |
| JOIN              | reserved | reserved |
| LEFT              | reserved | reserved |
| LIKE              | reserved | reserved |
| LOCALTIME         | reserved | reserved |
| LOCALTIMESTAMP    | reserved | reserved |
| NATURAL           | reserved | reserved |
| NORMALIZE         | reserved | reserved |
| NOT               | reserved | reserved |
| NULL              | reserved | reserved |
| ON                | reserved | reserved |
| OR                | reserved | reserved |
| ORDER             | reserved | reserved |
| OUTER             | reserved | reserved |
| PREPARE           | reserved | reserved |
| RECURSIVE         | reserved | reserved |
| RIGHT             | reserved | reserved |
| ROLLUP            | reserved | reserved |
| SELECT            | reserved | reserved |
| TABLE             | reserved | reserved |
| THEN              | reserved | reserved |
| TRUE              | reserved | reserved |
| UESCAPE           | reserved | reserved |
| UNION             | reserved | reserved |
| UNNEST            | reserved | reserved |
| USING             | reserved | reserved |
| VALUES            | reserved | reserved |
| WHEN              | reserved | reserved |
| WHERE             | reserved | reserved |
| WITH              | reserved | reserved |