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Apr 25, 2025
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Expression tags #1251

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98d4825
tags for days
JPryce-Aklundh Apr 25, 2025
9436a7d
fixes
JPryce-Aklundh Apr 25, 2025
657bd1b
bonus param fix
JPryce-Aklundh Apr 25, 2025
bde5ce1
Update modules/ROOT/pages/expressions/predicates/comparison-operators…
rsill-neo4j Apr 25, 2025
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15 changes: 13 additions & 2 deletions modules/ROOT/pages/clauses/where.adoc
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,13 +43,14 @@ CREATE (andy:Swedish:Person {name: 'Andy', age: 36}),
== Basic filtering

.Filter on a node label
// tag::clauses_where_node_label[]
[source, cypher]
----
MATCH (n)
WHERE n:Swedish
RETURN n.name AS name
----
// end::clauses_where_in_match_clause[]
// end::clauses_where_node_label[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -62,12 +63,14 @@ RETURN n.name AS name
|===

.Filter on a node property
// tag::clauses_where_node_property[]
[source, cypher]
----
MATCH (n:Person)
WHERE n.age < 35
RETURN n.name AS name, n.age AS age
----
// end::clauses_where_node_property[]

.Result
[role="queryresult",options="header,footer",cols="2*<m"]
Expand All @@ -80,12 +83,14 @@ RETURN n.name AS name, n.age AS age
|===

.Filter on a relationship property
// tag::clauses_where_relationship_property[]
[source, cypher]
----
MATCH (:Person {name:'Andy'})-[k:KNOWS]->(f)
WHERE k.since < 2000
RETURN f.name AS oldFriend
----
// end::clauses_where_relationship_property[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -112,12 +117,14 @@ To filter on a property using a dynamically computed name, use square brackets `
----

.Filter on a dynamically computed node property
// tag::clauses_where_dynamic[]
[source, cypher]
----
MATCH (n:Person)
WHERE n[$propname] > 40
RETURN n.name AS name, n.age AS age
----
// end::clauses_where_dynamic[]

.Result
[role="queryresult",options="header,footer",cols="2*<m"]
Expand Down Expand Up @@ -180,12 +187,14 @@ In this case, `name` is the only variable in scope for the `RETURN` clause.
=== Fixed-length patterns

.`WHERE` inside a node pattern
// tag::clauses_where_node_pattern[]
[source, cypher]
----
WITH 35 AS minAge
MATCH (a:Person WHERE a.name = 'Andy')-[:KNOWS]->(b:Person WHERE b.age > minAge)
RETURN b.name AS name
----
// end::clauses_where_node_pattern[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand Down Expand Up @@ -264,13 +273,15 @@ RETURN [(a)-[r:KNOWS WHERE r.since < minYear]->(b:Person) | r.since] AS years
If matching for variable length patterns, `WHERE` can only be used together with the xref:patterns/variable-length-patterns.adoc#quantified-path-patterns[quantified path pattern] or xref:patterns/variable-length-patterns.adoc#quantified-relationships[quantified relationships] syntax.

.Allowed - `WHERE` predicate inside a quantified relationship
// tag::clauses_where_var_length[]
[source, cypher]
----
MATCH p = (a:Person {name: "Andy"})-[r:KNOWS WHERE r.since < 2011]->{1,4}(:Person)
RETURN [n IN nodes(p) | n.name] AS paths
----
// end::clauses_where_var_length[]

Note that any path´s including `Timothy` and `Susan` are excluded by the `WHERE` predicate, since their incoming `KNOWS` relationships both have a `since` value that is higher than `2011.`
Note that any paths including `Timothy` and `Susan` are excluded by the `WHERE` predicate, since their incoming `KNOWS` relationships both have a `since` value that is higher than `2011.`

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand Down
9 changes: 9 additions & 0 deletions modules/ROOT/pages/expressions/conditional-expressions.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,7 @@ END
[[case-simple-examples]]
=== Example

// tag::expressions_conditional_expressions_simple[]
[source, cypher]
----
MATCH (n:Person)
Expand All @@ -85,6 +86,8 @@ CASE n.eyes
ELSE 3
END AS result, n.eyes
----
// end::expressions_conditional_expressions_simple[]


[role="queryresult",options="header,footer",cols="2*<m"]
|===
Expand Down Expand Up @@ -148,6 +151,7 @@ END
[[case-extended-simple-examples]]
=== Example

// tag::expressions_conditional_expressions_extended_simple[]
[source, cypher]
----
MATCH (n:Person)
Expand All @@ -162,6 +166,7 @@ CASE n.age
ELSE "Adult"
END AS result
----
// end::expressions_conditional_expressions_extended_simple[]

[role="queryresult",options="header,footer",cols="2*<m"]
|===
Expand Down Expand Up @@ -212,6 +217,7 @@ In this case, the predicate is tested to find a valid alternative.
[[case-generic-examples]]
=== Example

// tag::expressions_conditional_expressions_generic[]
[source, cypher]
----
MATCH (n:Person)
Expand All @@ -222,6 +228,7 @@ CASE
ELSE 3
END AS result, n.eyes, n.age
----
// end::expressions_conditional_expressions_generic[]

[role="queryresult",options="header,footer",cols="3*<m"]
|===
Expand Down Expand Up @@ -299,6 +306,7 @@ For more information about `null`, see xref:values-and-types/working-with-null.a

The results of a `CASE` expression can be used to set properties on a node or relationship.

// tag::expressions_conditional_expressions_properties[]
[source, cypher]
----
MATCH (n:Person)
Expand All @@ -311,6 +319,7 @@ END AS colorCode
SET n.colorCode = colorCode
RETURN n.name, n.colorCode
----
// end::expressions_conditional_expressions_properties[]

[role="queryresult",options="header,footer",cols="2*<m"]
|===
Expand Down
30 changes: 30 additions & 0 deletions modules/ROOT/pages/expressions/list-expressions.adoc
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Original file line number Diff line number Diff line change
Expand Up @@ -41,13 +41,15 @@ The subscript operator, `[]`, can be used to access specific elements in a `LIST
`[-1]` refers to the last element in a `LIST`, `[-2]` to the penultimate element, and so on.

.Access individual elements in a `LIST`
// tag::expressions_list_element_access[]
[source, cypher]
----
WITH [1, 2, 3, 4] AS list
RETURN list[0] AS firstElement,
list[2] AS thirdElement,
list[-1] AS finalElement
----
// end::expressions_list_element_access[]

.Result
[role="queryresult",options="header,footer",cols="3*<m"]
Expand Down Expand Up @@ -87,11 +89,13 @@ RETURN list[$myIndex] AS secondElement
|===

.Access a `LIST` within a nested `LIST`
// tag::expressions_list_nested_list_access[]
[source, cypher]
----
WITH [[1, 2], [3, 4], [5, 6]] AS nestedList
RETURN nestedList[1] AS secondList
----
// end::expressions_list_nested_list_access[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -104,12 +108,14 @@ RETURN nestedList[1] AS secondList
|===

.Access specific elements in a nested `LIST`
// tag::expressions_list_nested_list_specific_element_access[]
[source, cypher]
----
WITH [[1, 2], [3, 4], [5, 6]] AS nestedList
RETURN nestedList[1] AS secondList,
nestedList[1][0] AS firstElementOfSecondList
----
// end::expressions_list_nested_list_specific_element_access[]

.Result
[role="queryresult",options="header,footer",cols="2*<m"]
Expand Down Expand Up @@ -189,13 +195,15 @@ This allows for extracting a subset of a `LIST` rather than a single element.
List slicing is inclusive at the start of the range, but exclusive at the end (e.g. `list[start..end]` includes `start`, but excludes `end`).

.Slice operations on a `LIST`
// tag::expressions_list_slicing[]
[source, cypher]
----
WITH [1, 2, 3, 4, 5, 6] AS list
RETURN list[2..4] AS middleElements,
list[..2] AS noLowerBound,
list[2..] AS noUpperBound
----
// end::expressions_list_slicing[]

.Result
[role="queryresult",options="header,footer",cols="3*<m"]
Expand All @@ -210,13 +218,15 @@ RETURN list[2..4] AS middleElements,
Negative indexing in list slicing references elements from the end of the `LIST`; `..-1` excludes the last element, `..-2` excludes the last two elements, and so on.

.Negative indexing and list slicing
// tag::expressions_list_negative_slicing[]
[source, cypher]
----
WITH [1, 2, 3, 4, 5, 6] AS list
RETURN list[..-1] AS finalElementRemoved,
list[..-2] AS finalTwoElementsRemoved,
list[-3..-1] AS removedFirstThreeAndLast
----
// end::expressions_list_negative_slicing[]

.Result
[role="queryresult",options="header,footer",cols="3*<m"]
Expand Down Expand Up @@ -251,11 +261,13 @@ RETURN nestedList[0..2] AS slicedNestedList
Slicing inner `LIST` values require two `[]` operators; the first `[]` accesses elements from the outer `LIST`, while the second slices or accesses elements from the inner `LIST`.

.Slice inner `LIST`
// tag::expressions_list_slice_inner_list[]
[source, cypher]
----
WITH [[1, 2, 3], [4, 5, 6], [7, 8, 9]] AS nestedList
RETURN nestedList[1][0..2] AS slicedInnerList
----
// end::expressions_list_slice_inner_list[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand Down Expand Up @@ -293,11 +305,13 @@ Cypher contains two list concatenation operators: `||` and `+`.
`||` is xref:appendix/gql-conformance/index.adoc[GQL conformant], while `+` is not.

.List concatenation using `||` and `+`
// tag::expressions_list_concatenation[]
[source, cypher]
----
RETURN [1,2] || [3,4] AS list1,
[1,2] + [3,4] AS list2
----
// end::expressions_list_concatenation[]

.Result
[role="queryresult",options="header,footer",cols="2*<m"]
Expand Down Expand Up @@ -353,12 +367,14 @@ The `+` operator can add elements to the beginning or end of a `LIST` value.
This is not possible using the `||` operator.

.Add elements to the beginning and end of a `LIST`
// tag::expressions_list_add_elements[]
[source, cypher]
----
WITH [1, 2, 3, 4] AS list
RETURN 0 + list AS newBeginning,
list + 5 AS newEnd
----
// end::expressions_list_add_elements[]

.Result
[role="queryresult",options="header,footer",cols="2*<m"]
Expand Down Expand Up @@ -458,11 +474,13 @@ RETURN [x IN range(0,5) | x * 10] AS result


.List comprehension with both an expression and filtering
// tag::expressions_list_comprehension[]
[source, cypher]
----
WITH [1, 2, 3, 4, 5] AS list
RETURN [n IN list WHERE n > 2 | n] AS filteredList
----
// end::expressions_list_comprehension[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand Down Expand Up @@ -498,13 +516,15 @@ RETURN [listIndex IN range(0, size(list)-1) | toString(listIndex) || ': ' || toS
The below query iterates over the `skills` property of each `Person` node and creates a new `LIST` by xref:expressions/string-operators.adoc[concatenating the `STRING`] `" expert"` to each element in `skills`.

.Modify `LIST` properties using list comprehension
// tag::expressions_list_comprehension_properties[]
[source, cypher]
----
MATCH (p:Person) WHERE p.skills IS NOT NULL
ORDER BY p.name
RETURN p.name AS name,
[skill IN p.skills | skill + " expert"] AS modifiedSkills
----
// end::expressions_list_comprehension_properties[]

.Result
[role="queryresult",options="header,footer",cols="2*<m"]
Expand All @@ -524,11 +544,13 @@ RETURN p.name AS name,
The next query uses the xref:functions/aggregating.adoc#functions-collect[`collect()`] function to gather all `Person` nodes into a `LIST`, and the `WHERE 'Python' IN person.skills` predicate filters that list to include only those nodes whose `skills` property contains `Python`.

.List comprehension with a `WHERE` predicate
// tag::expressions_list_comprehension_where[]
[source, cypher]
----
MATCH (p:Person)
RETURN [person IN collect(p) WHERE 'Python' IN person.skills | person.name] AS pythonExperts
----
// end::expressions_list_comprehension_where[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -543,10 +565,12 @@ RETURN [person IN collect(p) WHERE 'Python' IN person.skills | person.name] AS p
List comprehension can be used to remove any unknown `NULL` values when concatenating `LIST` values.

.List comprehension to remove `NULL` values during list concatenation
// tag::expressions_list_comprehension_concatenation_remove_null[]
[source, cypher]
----
RETURN [x IN ([1, null, 3] || [null, 5, null]) WHERE x IS NOT NULL] AS listWithoutNull
----
// end::expressions_list_comprehension_concatenation_remove_null[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -572,11 +596,13 @@ Pattern comprehension is used to create new `LIST` values by matching graph patt
The below query retrieves a list of names of people who work for `Alice` by using pattern comprehension extract the names of `employees` into a `LIST`.

.Pattern comprehension on a fixed-length pattern
// tag::expressions_list_pattern_comprehension[]
[source, cypher]
----
MATCH (alice:Person {name: 'Alice'})
RETURN [(employee:Person)-[:WORKS_FOR]->(alice) | employee.name] AS employees
----
// end::expressions_list_pattern_comprehension[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -591,11 +617,13 @@ RETURN [(employee:Person)-[:WORKS_FOR]->(alice) | employee.name] AS employees
Pattern comprehensions can include `WHERE` predicates.

.Pattern comprehension including a `WHERE` predicate
// tag::expressions_list_pattern_comprehension_where[]
[source, cypher]
----
MATCH (alice:Person {name: 'Alice'})
RETURN [(employee:Person)-[:WORKS_FOR]->(alice) WHERE employee.age > 30 | employee.name || ', ' || toString(employee.age)] AS employeesAbove30
----
// end::expressions_list_pattern_comprehension_where[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand All @@ -622,6 +650,7 @@ The below query uses a pattern comprehension to collect the skills of all superi
The xref:functions/list.adoc#functions-reduce[`reduce()`] function concatenates these skills into a single `LIST`, and xref:clauses/unwind.adoc[`UNWIND`] is used to flatten this `LIST` before returning the distinct skills in a new `LIST`.

.Allowed: variable-length pattern comprehension using variable-length relationship syntax
// tag::expressions_list_pattern_comprehension_var_length[]
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@rsill-neo4j rsill-neo4j Apr 25, 2025

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this one and contains lines that are so long that they don't render nicely in the cheat sheet 🤔
it's a minor thing (formatting)

[source, cypher]
----
MATCH (cecil:Person {name: 'Cecil'})
Expand All @@ -630,6 +659,7 @@ WITH reduce(accumulatedSkills = [], superiorSkills IN allSuperiorsSkills | accum
UNWIND allSkills AS superiorsSkills
RETURN collect(DISTINCT superiorsSkills) AS distinctSuperiorsSkills
----
// end::expressions_list_pattern_comprehension_var_length[]

.Result
[role="queryresult",options="header,footer",cols="1*<m"]
Expand Down
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