Logical operators

seekdb supports common logical operators.

Overview of logical operators

The following table describes the logical operators supported in the current version of seekdb.

Operator	Operands	Description
NOT/!	Unary	Logical NOT
AND/&&	Binary	Logical AND
OR/`		`
XOR	Multiple	Logical XOR

Description

In SQL, the result of any logical operator is TRUE, FALSE, or NULL (UNKNOWN). In seekdb, they are implemented as 1 (TRUE), 0 (FALSE), and NULL, and any non-zero, non-NULL value is evaluated as TRUE.

Limitations

The ANY operator is supported only for array data types. For more information about the usage and examples, see Array decision functions.

NOT/!

If the operand is 0, the result is 1. If the operand is non-zero, the result is 0, and NOT NULL returns NULL.

Here is an example:

SELECT NOT NULL;
+----------+
| NOT NULL |
+----------+
|     NULL |
+----------+
1 row in set (0.001 sec)

SELECT ! (1+1);
+---------+
| ! (1+1) |
+---------+
|       0 |
+---------+
1 row in set (0.001 sec)

AND/&&

If all operands are non-zero and not NULL, the result is 1. If one or more operands are 0, the result is 0. Otherwise, NULL is returned.

Here is an example:

SELECT 1 AND NULL;
+------------+
| 1 AND NULL |
+------------+
|       NULL |
+------------+
1 row in set (0.001 sec)

SELECT 0 AND NULL;
+------------+
| 0 AND NULL |
+------------+
|          0 |
+------------+
1 row in set (0.000 sec)

OR/||

If both operands are not NULL, the result is 1 if any operand is non-zero, otherwise 0. For NULL operands, if the other operand is non-zero, the result is 1; otherwise, NULL is returned. If both operands are NULL, the result is NULL.

Here is an example:

SELECT 0 OR NULL;
+-----------+
| 0 OR NULL |
+-----------+
|      NULL |
+-----------+
1 row in set (0.001 sec)

SELECT 1 OR NULL;
+-----------+
| 1 OR NULL |
+-----------+
|         1 |
+-----------+
1 row in set (0.000 sec)

XOR

If any operand is NULL, NULL is returned. For non-NULL operands, if an odd number of operands are non-zero, the result is 1; otherwise, 0 is returned.

Here is an example:

SELECT 1 XOR NULL;
+------------+
| 1 XOR NULL |
+------------+
|       NULL |
+------------+
1 row in set (0.001 sec)

SELECT 1 XOR 1 XOR 1;
+---------------+
| 1 XOR 1 XOR 1 |
+---------------+
|             1 |
+---------------+
1 row in set (0.001 sec)

info

a XOR b is mathematically equivalent to (a AND (NOT b)) OR ((NOT a) and b).