Keywords

The SQL contains reserved and non-reserved words. Standards require that reserved keywords not be used as other identifiers. Non-reserved keywords have special meanings only in a specific environment and can be used as identifiers in other environments.

The naming rules for identifiers are as follows:

• An identifier name can only contain letters, underscores, digits (0-9), and dollar signs ($).

• An identifier name must start with a letter (a to z) or an underscore (_).

  NOTE:

  • The naming rules are recommended but not mandatory.

  • In special cases, double quotation marks (") can be used to avoid special character errors.

Compared with the original openGauss, Dolphin modifies keywords as follows:

1. MEDIUMINT is added as a non-reserved keyword.
2. The keyword DATE can be used as a function.
3. LAST_DAY is added as a reserved keyword to distinguish the original LAST_DAY function of openGauss from the LAST_DAY function of Dolphin at the syntax level.
4. GET_FORMAT is added as a non-reserved keyword to identify the GET_FORMAT function in syntax.
5. DAY_HOUR, DAY_MINUTE, DAY_SECOND, DAY_MICROSECOND, HOUR_MINUTE, HOUR_SECOND, HOUR_MICROSECOND, MINUTE_SECOND, MINUTE_MICROSECOND, and SECOND_MICROSECOND are added as non-reserved keywords for the EXTRACT function to identify the corresponding unit in syntax.

Table 1 SQL keywords