42I80

Status description

error: syntax error or access rule violation - invalid grouping element. The grouping element { $expr } is not a valid grouping key. { $cause }

Explanation

The GROUP BY clause is used to group the results of a clause by one or more expressions. Each expression in the GROUP BY clause is called a grouping element.

A grouping element may reference an alias introduced by the same WITH or RETURN clause only if the grouping element is exactly that alias.
A non-simple grouping element, such as a property access, a function call, or an arithmetic expression, cannot contain an alias.
A grouping element cannot contain an aggregation result, since aggregations are computed per group and cannot be grouping keys.

Example scenarios

Let’s take the following example scenarios:

Invalid grouping on projection item alias

Try projecting b AS a, so that a is a projection item alias that shadows the incoming a, and then grouping by a.p — a property access on that alias:

UNWIND [{a: {p: 1}, b: 20}, {a: {p: 2}, b: 10}] AS row
WITH row.a AS a, row.b AS b
RETURN b AS a, count(*) AS cnt
  GROUP BY a.p;

Because a is a projection item alias, the only valid way to group by it is the simple reference a; the property access a.p is not a valid grouping element. The query returns a chain of errors where GQLSTATUS 42I80 is the cause of GQLSTATUS 42001:

GQLSTATUS error chain

42I80: syntax error or access rule violation - invalid grouping element. The grouping element 'a.p' is not a valid grouping key. A grouping element that references the projection item alias `a` must be a simple variable reference. (line 4, column 13 (offset: 126))
"  GROUP BY a.p"
             ^
  42001: syntax error or access rule violation - invalid syntax

To fix the query, the preferred way is to reference the alias as a simple variable:

Group by the alias as a simple variable

UNWIND [{a: {p: 1}, b: 20}, {a: {p: 2}, b: 10}] AS row
WITH row.a AS a, row.b AS b
RETURN b AS a, count(*) AS cnt
  GROUP BY a;

To group on the incoming value, rename the projection item so it no longer shadows the incoming variable, then group by that expression:

Avoid shadowing the incoming variable

UNWIND [{a: {p: 1}, b: 20}, {a: {p: 2}, b: 10}] AS row
WITH row.a AS a, row.b AS b
RETURN b AS bb, count(*) AS cnt
  GROUP BY a.p;

Grouping element references an aggregation result

Try grouping by the aggregation alias cnt:

UNWIND [{a: 1}, {a: 2}] AS row
WITH row.a AS a
RETURN a, count(*) AS cnt
  GROUP BY a, cnt;

The query returns a chain of errors where GQLSTATUS 42I80 is the cause of GQLSTATUS 42001:

GQLSTATUS error chain

42I80: syntax error or access rule violation - invalid grouping element. The grouping element 'cnt' is not a valid grouping key. A grouping element cannot reference the aggregation `cnt`. (line 4, column 15 (offset: 87))
"  GROUP BY a, cnt"
               ^
  42001: syntax error or access rule violation - invalid syntax

To resolve the error remove the aggregation result from the grouping elements:

Group only by non-aggregating expressions

UNWIND [{a: 1}, {a: 2}] AS row
WITH row.a AS a
RETURN a, count(*) AS cnt
  GROUP BY a;

Glossary

$action: Freeform description of an action.
$alias: An alias name, mydb-alias.
$aliasList: A list of alias names, for example, mydb-alias1, mydb-alias2.
$allocType: Allocation type (primary or secondary).
$arg: Procedure or function argument, for example, database, pause, dryrun, etc.
$argList: A list of procedure or function arguments, for example, edition, name and versions.
$argType: Argument type, either input or output.
$auth: Auth provider name, for example, ldap, native.
$authRule: ABAC auth rule name.
$boltServerState: Bolt server state, for example, READY.
$boltMsgLenLimit: Bolt message length limit, for example, 1000.
$bytes: Number of bytes.
$cause: Freeform description of what caused the error.
$cfgSetting: Configuration setting key, for example, server.https.enabled.
$clause: A Cypher clause, for example, USE, MATCH.
$clause: A list of Cypher clauses, for example, USE, MATCH.
$cmd: A Cypher command, for example, DROP DATABASE, PROFILE, SHOW PROCEDURES.
$component: A component of something, for example, hours/minutes within a time, a subset input within the whole input, TOPOLOGY clause within the whole CREATE/ALTER DB … SET TOPOLOGY, etc.
$constr: Constraint name, for example, book_isbn.
$constrDescrOrName: Constraint description, (:Label {property0, property1, property2, property1, property3}).
$context: Freeform description of a context, where something is invalid or unsupported, OPTIONS, URL, username, etc.
$coordinates: Coordinate value, for example, [3.15, 4.012, 5.905].
$count: Number of something, for example, 3.
$countAllocs: Desired number of servers to use.
$countSeeders: Number of seeding servers.
$crs: Coordinate reference system, for example, WGS84.
$db: Database name, for example, myDb.
$dbList: A list of database names.
$dim: Number representing index or point dimenionality.
$edition: Neo4j edition, for example, Community or Enterprise.
$endpointType: One of start or end of a relationship.
$entityId: ID of a node or a relationship.
$entityType: A node or a relationship.
$expr: Cypher expression, for example, 1 + n.prop.
$exprType: Freeform expression type, for example, EXISTS, COUNT, COLLECT.
$feat: Freeform feature description.
$field: Input field, for example, of a procedure, function, or deserialization.
$fun: Function name, for example, collect().
$funClass: User-defined function implementation class name, for example, MyFunctionClass.
$funType: Function type, e.g. non-deterministic or aggregate.
$graph: The name of a graph, for example, myGraph.
$graphTypeDependence: Graph type dependencency for constraint, one of UNDESIGNATED, INDEPENDENT, or DEPENDENT.
$graphTypeElement: An element of a graph type, for example (:Node ⇒ { name :: STRING}), or (:Source)-[:REL ⇒]→(:Target).
$graphTypeReference: Graph type reference, for example, (:Node ⇒) or p.
$graphTypeOperation: Graph type operation, for example, one of SET, ADD, DROP or ALTER.
$groupingConstructs: Constructs that establish a grouping and thereby restrict which variables remain accessible, for example, DISTINCT, an aggregation, or a GROUP BY clause.
$hint: Freeform description of a hint, for example, USING INDEX n:N(prop).
$hintList: A list of free form descriptions of hints like USING INDEX n:N(prop).
$ident: A generic identifier, for example my_identifier.
$idx: Index name, my_index.
$idxDescr: Index description, for example, INDEX :Person(name).
$idxDescrOrName: Index descriptor or name.
$idxOrConstr: Index or constraint name, for example, my_index or book_isbn.
$idxOrConstrPat: Index or constraint pattern, for example, CREATE CONSTRAINT bar IF NOT EXISTS FOR (n:L) REQUIRE (n.p1) IS NODE KEY.
$idxType: Index type, for example, text, vector, etc.
$input: Piece of user input.
$inputList: A list of user inputs.
$item: Freeform description of an item.
$keyword: Cypher keyword, for example, MERGE.
$label: Label name, for example, Person.
$labelExpr: Label expression, for example, (n:Movie|Person).
$labelList: A list of label names, for example, Person, Actor.
$lower: The lowest accepted number of a range.
$mapKey: Map key.
$mapKeyList: A list of map keys, for example, first and second in the map {first: 1, second: 2}.
$matchMode: GPM match mode, for example, REPEATABLE ELEMENTS.
$msg: Freeform message.
$msgTitle: Freeform message title.
$namespaceList: A list of namespaces of procedures, for example, apoc.math..
$operation: A mathematical operation, for example, / by zero, >.
$option: Option name
$optionList: A list of option names.
$param: Parameter name, for example, $pattern.
$paramList: A list of parameters, for example $pattern, $prop.
$pat: Pattern, for example, (:Person).
$pathMode: GPM path mode, for example, ACYCLIC.
$pathModeList: A list of GPM path modes, for example, TRAIL, ACYCLIC.
$port: Port name, for example, 6362.
$portList: A list of port names, for example, 6362, 6000, 7000.
$pos: A position, for example, in a sequence, for example, 2
$pred: A predicate, for example, x = 3.
$predList: A list of predicates, for example, 'x = 3', 'y > 4'.
$preparserInput: Piece of preparser input.
$proc: Procedure name, for example, db.labels().
$procClass: User-defined procedure implementation class name, for example, MyProcedureClass.
$procExeMode: Procedure execution mode, one of READ, WRITE, SCHEMA, and DBMS.
$procField: User-defined procedure implementation class argument name, for example, myArgument.
$procFieldType: User-defined procedure implementation class argument type, one of input or output.
$procFun: Procedure or function name or ID, for example, db.labels() or collect().
$procMethod: User-defined procedure implementation class method name, for example, myProcedureMethod
$procParam: User-defined procedure implementation parameter name.
$procParamFmt: Freeform user-defined procedure implementation parameter format, for example, com.example.*.
$propKey: Property key name, for example, name.
$propKeyList: A list of property key names, for example, name, age, hometown.
$query: A statement that retrieves or writes information to a database, for example, MATCH (n) WHERE n.prop.
$reasonList: A list of reasons of the failure.
$relType: Relationship type name, for example, KNOWS.
$replacement: A free-form text, a replacement of a deprecated feature, a Cypher command, etc.
$role: RBAC role name, for example, admin, public, receptionist.
$routingPolicy: Routing policy name.
$runtime: Cypher runtime name. One of slotted, pipelined, and parallel.
$schemaDescr: Schema descriptor, for example, (:Label1 {prop1}).
$schemaDescrType: Freeform type of schema descriptor, for example, label property existence constraint.
$selector: GPM path selector, for example, ALL PATHS, SHORTEST 2, etc.
$selectorOrPathMode: GPM path selector, for example, ALL PATHS, SHORTEST 2, etc, or GPM path mode, for example ACYCLIC, TRAIL, etc.
$selectorType: Selector type.
$server: Server name or ID, for example, 25a7efc7-d063-44b8-bdee-f23357f89f01.
$serverList: A list of server names or IDs, for example, 'server-1', 'server-2'.
$serverType: Server type, PRIMARY (primaryConstrained), SECONDARY (secondaryConstrained), or NONE.
$serverAddress: Server address, for example, localhost:20025.
$sig: Procedure or function signature, for example, date(input = DEFAULT_TEMPORAL_ARGUMENT :: ANY) :: DATE
$storeFormat: Store format name. One of "aligned", "block", "standard", "high_limit".
$syntax: Cypher syntax or keyword.
$temporal: Temporal value, for example, 2025-02-18.
$timeAmount: Integral amount of time unit (a number).
$timeUnit: Common time unit name, for example, seconds, minutes, hours.
$token: Token name, for example, MyLabel, MyRelationshipType, myPropertyKey.
$tokenId: Token ID.
$tokenType: One of a label, a relationship type, or a property key.
$transactionId: The transaction ID of a running query.
$typeDescription: Freeform description of a type e.g. 'a list'.
$upper: The highest accepted number of a range.
$url: A URL, for example, https://example.com.
$user: A user name, for example, neo4j.
$value: Some value.
$valueList: A list of values.
$valueType: Cypher value type, for example, STRING, BOOLEAN, INTEGER, LIST<STRING>, etc.
$valueTypeList: A list of Cypher value types.
$variable: Variable name, for example, n.
$variableList: A list of variable names, for example, a, b, c.
$version: A version, for example, 25 in CYPHER 25.