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 MogDB, 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 MogDB from the LAST_DAY function of Dolphin at the syntax level.

Table 1 SQL keywords

Keyword	MogDB	SQL:1999	SQL-92
FORMAT	Non-reserved (excluding functions and types)	-	-
IF	Non-reserved (excluding functions and types)	-	-
KEYS	Non-reserved	-	-
MEDIUMINT	Non-reserved (excluding functions and types)	-	-
SIGNED	Non-reserved (excluding functions and types)	-	-
UNSIGNED	Non-reserved (excluding functions and types)	-	-
ZEROFILL	Non-reserved	-	-
DATE	Non-reserved (a function or type)	-	-
LAST_DAY	Reserved	-	-