Logical Operators

M-compatible databases support four logical operators: AND (&&), OR (||), NOT (!), and XOR. For details, see Table 1. There are three types of operation results: TRUE, FALSE, and NULL.

**Table 1** Logical operator details
Operator	Operand	Description
NOT/!	Unary	NOT.
AND/&&	Binary	AND.
OR/\|\|	Binary	OR.
XOR	Binary	XOR.

NOT and AND, OR, and XOR list the calculation rules, where a and b represent logical expressions.

NOT

If the operand is TRUE, the calculation result is FALSE. If the operand is FALSE, the calculation result is TRUE.

Value range: Boolean

The following lists calculation rules.

**Table 2** NOT calculation rules (calculation based on TRUE, FALSE, and NULL)
a	NOT a
TRUE	FALSE
FALSE	TRUE
NULL	NULL

The operators ! and NOT have the same function, but the priority of the operator ! is higher than that of NOT.

Examples:

m_db=# SELECT NOT TRUE;
 ?column? 
----------
 f
(1 row)

m_db=# SELECT NOT FALSE;
 ?column? 
----------
 t
(1 row)

m_db=# SELECT NOT NULL;
 ?column? 
----------
 
(1 row)

AND, OR, and XOR

The calculation logic of AND, OR, and XOR is listed in the following table.

**Table 3** Operation rules of AND, OR, and XOR (calculation based on TRUE, FALSE, and NULL)
a	b	Result of a AND b	Result of a OR b	Result of a XOR b
TRUE	TRUE	TRUE	TRUE	FALSE
TRUE	FALSE	FALSE	TRUE	TRUE
TRUE	NULL	NULL	TRUE	NULL
FALSE	FALSE	FALSE	FALSE	FALSE
FALSE	NULL	FALSE	NULL	NULL
NULL	NULL	NULL	NULL	NULL

The operators AND, XOR, and OR are commutative, that is, you can switch the left and right operand without affecting the result.

Examples:

m_db=# SELECT TRUE AND TRUE;
 ?column? 
----------
 t
(1 row)

m_db=# SELECT TRUE OR FALSE;
 ?column? 
----------
 t
(1 row)

m_db=# SELECT TRUE XOR NULL;
 ?column? 
----------
 
(1 row)

Specification Constraints of Logical Operators

Logical operations support all data types supported by the current M-compatible database. During data operations between different major types, the data is promoted to the major type first, and then the calculation is performed based on whether the result of the promoted major type is 0. The following table lists the promotion rules.

**Table 4** Logical operation type classification
Operator	Left and Right Input Parameter Type	Classification Type
XOR	All types	BIGINT
AND, OR, and NOT	TINYINT, SMALLINT, MEDIUMINT, INT/INTEGER, BIGINT, TINYINT UNSIGNED, SMALLINT UNSIGNED, MEDIUMINT UNSIGNED, INT/INTEGER UNSIGNED, BIGINT UNSIGNED, BIT, YEAR, and BOOL/LBOOLEAN	BIGINT
AND, OR, and NOT	Others	DOUBLE