Operators

GaussDB is basically compatible with operators in Oracle Database.

SQL Operators

**Table 1** SQL operators
No.	Oracle Database	GaussDB
1	Unary and binary operators	Supported.
2	Operator precedence	Supported.

Arithmetic Operators

**Table 2** Arithmetic operators
No.	Oracle Database	GaussDB
1	Unary operators: positive (+) and negative (–).	Supported.
2	Binary operators: addition (+) and subtraction (–).	Supported.
3	Binary operators: multiplication (*) and division (/).	Supported.

COLLATE Operator

**Table 3** COLLATE operator
No.	Oracle Database	GaussDB
1	COLLATE collation_name	Supported.

Connection Operators

**Table 4** Connection operators
No.	Oracle Database	GaussDB
1	\|\|	Supported.

Hierarchical Query Operators

**Table 5** Hierarchical query operators
No.	Oracle Database	GaussDB	Difference
1	prior	Supported, with differences.	GaussDB: Only common columns can be called. Functions cannot be called.
2	connect_by_root	Supported, with differences.	GaussDB: When connect_by_root is called, if parentheses are used to modify the operation value, the behavior is the same as that of Oracle Database. If parentheses are not used, this operator can be called only for common columns.
3	connect_by_iscycle	Supported, with differences.	It can be used independently in GaussDB and must be used together with NOCYCLE in Oracle Database.
4	start with, connect by, and level	Supported, with differences.	In GaussDB, start with, connect by, and level can be used as column aliases, but they cannot be used as column aliases in Oracle Database.
5	start with	Supported, with differences.	In GaussDB, start with can be followed by an empty string for query, and the query result is empty. Operations on pseudocolumns are supported. In Oracle Database, an error is reported in these cases.
6	connect by	Supported, with differences.	In GaussDB, connect by can be used with NULL values. In Oracle Database, an error is reported.

Set Operators

**Table 6** Set operators
No.	Oracle Database	GaussDB
1	union	Supported.
2	union all	Supported.
3	intersect	Supported.
4	minus	Supported.

Multiset Operators

**Table 7** Multiset operators
No.	Oracle Database	GaussDB
1	multiset except	Supported.
2	multiset intersect	Supported.
3	multiset union	Supported.

User-defined Operators

**Table 8** User-defined operators
No.	Oracle Database	GaussDB	Difference
1	CREATE OPERATOR	Supported, with differences.	Oracle Database provides CONTEXT_CLAUSE to define functional evaluation functions, which is different from GaussDB that constrains selectivity evaluation functions. GaussDB does not support user-defined functional evaluation functions. Optional parameters in Oracle Database differ greatly from those in GaussDB. For details, see the GaussDB parameter description in "SQL Reference > SQL Syntax > C > CREATE OPERATOR" in Developer Guide.

Comparison Operators

No.	Oracle Database	GaussDB
1	< =	Supported.
2	< >	Supported.
3	> =	Supported.
4	^ =	Supported.
5	! =	Not supported. For !=, if there is a space between an exclamation mark (!) and an equal sign (=), the exclamation mark will be identified as factorial.

For comparison operators <=, <>, >=, and ^=, if there is a space between two symbols, it does not affect normal operations. For !=, if there is a space between an exclamation mark (!) and an equal sign (=), the exclamation mark will be identified as factorial, which may cause the result to be inconsistent with the expected result.

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