Comparison predicate¶
The comparison predicate compares two values and returns true if the comparison is true, false if the comparison is false, and null if any of the values is null.
Syntax¶
- comparison_predicate
- comp_op
comparison_predicate ::=
comparison_predicand comp_op comparison_predicand
comp_op ::= '=' | '<>' | '<' | '>' | '<=' | '>='
Parameters¶
comparison_predicand¶
A value that is compared with another value.
The values to be compared must be of the same value type; otherwise, the error NR002 is returned indicating an undefined function.
comp_op¶
The operator that is used to compare two values.
The applicable operator differs depending on the value type. The following table lists the operators that can be used with each value type:
| Value type | Operator | Description |
|---|---|---|
| Numeric value | =, <>, <, >, <=, >= |
The comparison follows the mathematical rules. |
| String value | =, <>, <, >, <=, >= |
The comparison is based on lexicographical byte-wise order. |
| Boolean value | =, <>, <, >, <=, >= |
The comparison follows the rule that true is greater than false. |
| Null value | =, <>, <, >, <=, >= |
Any comparison with a null value returns null. |
| Temporal instant value | =, <>, <, >, <=, >= |
The comparison is based on the chronological order. |
| Temporal duration value | =, <>, <, >, <=, >= |
The comparison is based on the duration of time. |
| List value | =, <> |
The comparison that whether the elements of two lists are the same. It returns true if the two lists have the same elements in the same order, and false otherwise. |
| Set value | =, <> |
The comparison that whether the elements of two sets are the same. It returns true if the two sets have the same elements, and false otherwise. |
| Map value | =, <> |
The comparison that whether the key-value pairs of two maps are the same. It returns true if the two maps have the same key-value pairs, and false otherwise. |
| Record value | =, <> |
The comparison that whether the field names and values of two records are the same. It returns true if the two records have the same fields with the same values, and false otherwise. |
| Graph element value | =, <> |
The comparison that whether two graph elements are the same. It returns true if the two graph elements are the same, and false otherwise. |
| Path value | =, <> |
The comparison that whether two paths are the same. It returns true if the two paths are the same, and false otherwise. |
| Spatial value | =, <> |
The comparison that whether two spatial values are the same. It returns true if the two spatial values are the same, and false otherwise. |
Examples¶
The following examples are based on the example dataset.
Compare strings¶
LET l1= 'w55', l2='e34' RETURN l1 > l2 AS a
Return:
+------+
| a |
+------+
| true |
+------+
Compare boolean values¶
RETURN (2>1) > (1>2) AS a, (2>1) <= (3>2) AS b
Return:
+------+------+
| a | b |
+------+------+
| true | true |
+------+------+
Compare null values¶
'''
RETURN null > (1>2) AS a,
null >= 1 AS b,
null < "String" AS c,
null = LIST[1,2,3] AS d,
null < local_datetime("2012-03-04T05:06:07.0890") AS e,
null <> RECORD{} AS f
'''
Return:
+------+------+------+------+------+------+
| a | b | c | d | e | f |
+------+------+------+------+------+------+
| null | null | null | null | null | null |
+------+------+------+------+------+------+
Compare list values¶
LET l1= LIST[1,2,3], l2=LIST[1,2,3.5] RETURN l1 = l2 AS a
Return:
+-------+
| a |
+-------+
| false |
+-------+
Compare temporal instant values¶
LET t1=local_datetime("2012-03-04T05:06:07.0890"), t2=local_datetime("2012-03-02T05:06:07.0") RETURN t1 > t2 AS a
Return:
+------+
| a |
+------+
| true |
+------+
Compare temporal duration values¶
LET d1=duration({years:1, months:2}), d2=duration({years:1, months:3}) RETURN d1 < d2 AS a
Return:
+------+
| a |
+------+
| true |
+------+
Compare record values¶
LET r1 = {a:1, b:true, c:"str"}, r2 = {a:1, c:"str", b:true} RETURN r1 = r2 AS a
Return:
+------+
| a |
+------+
| true |
+------+
Compare graph element values¶
'''
USE movie
MATCH (v1@Director)->(m1), (v2@Director)->(m2)
WHERE m1.name = "Saw III" AND m2.name = "Saw IV"
RETURN v1 = v2 AS a
'''
The preceding statement selects the directors of the movies "Saw III" and "Saw IV" and compares whether they are the same person.
Return:
+------+
| a |
+------+
| true |
+------+
Compare path values¶
'''
USE movie
MATCH p1 = (m1@Movie)<-(u1@`User`),
p2 = (m2@Movie)<-(u2@`User`)
WHERE u1.id = u2.id
RETURN p1 = p2 AS a, m1.name, m2.name
LIMIT 5
'''
The preceding statement selects the paths that start from the same user and end at movies, and compares whether the paths are the same.
Return:
+-------+--------------------------------------------------------+--------------------------------------------------------+
| a | m1.name | m2.name |
+-------+--------------------------------------------------------+--------------------------------------------------------+
| false | Simpsons | Pirates of the Caribbean: The Curse of the Black Pearl |
| false | Simpsons | Harry Potter and the Philosopher's Stone |
| false | Simpsons | Pi |
| false | Pirates of the Caribbean: The Curse of the Black Pearl | Simpsons |
| false | Pirates of the Caribbean: The Curse of the Black Pearl | Harry Potter and the Philosopher's Stone |
+-------+--------------------------------------------------------+--------------------------------------------------------+
Compare spatial values¶
'''
LET l1= ST_GeogFromText ('POINT (34.0522 -18.2437) '),
l2=ST_GeogFromText ('POINT (34.0522 -18.2437) ')
RETURN l1 = l2 AS a, l1 <> l2 AS b
'''
Return:
+------+-------+
| a | b |
+------+-------+
| true | false |
+------+-------+
Compare set values¶
LET l1 = SET {1,2,3}, l2 = SET {1,2,3.5} RETURN l1 = l2 AS a, l1 <> l2 AS b
Return:
+-------+------+
| a | b |
+-------+------+
| false | true |
+-------+------+
Compare map values¶
LET m1 = MAP {'a':1, 'b':2}, m2 = MAP {'b':2, 'a':1, 'b': 3} RETURN m1 = m2 AS a, m1 <> m2 AS b
Return:
+------+-------+
| a | b |
+------+-------+
| true | false |
+------+-------+