10.4. Start
Every query describes a pattern, and in that pattern one can have multiple starting points. A starting point is a relationship or a node where a pattern is anchored. You can either introduce starting points by id, or by index lookups. Note that trying to use an index that doesn’t exist will generate an error.
Note
|
This is the graph the examples are using:
Get node or relationship from index
Node by index lookup
When the starting point can be found by using index lookups, it can be done like this: node:index-name(key = "value")
. In this example, there exists a node index named nodes
.
Query.
START n=node:nodes(name = "A") RETURN n
The query returns the node indexed with the name "A
".
Result
n |
---|
1 row |
|
Relationship by index lookup
When the starting point can be found by using index lookups, it can be done like this: relationship:index-name(key = "value")
.
Query.
START r=relationship:rels(name = "Andrés") RETURN r
The relationship indexed with the name
property set to "Andrés
" is returned by the query.
Result
r |
---|
1 row |
|
Node by index query
When the starting point can be found by more complex Lucene queries, this is the syntax to use: node:index-name("query")
.This allows you to write more advanced index queries.
Query.
START n=node:nodes("name:A") RETURN n
The node indexed with name "A" is returned by the query.
Result
n |
---|
1 row |
|
Get node or relationship by id
Node by id
Binding a node as a starting point is done with the node(*)
function.
Note Neo4j reuses its internal ids when nodes and relationships are deleted, which means it’s bad practice to refer to them this way. Instead, use application generated ids. |
Query.
START n=node(0) RETURN n
The corresponding node is returned.
Result
n |
---|
1 row |
|
Try this query live. create (_0 {`name`:"A"}) create (_1 {`name`:"B"}) create (_2 {`name`:"C"}) create _0-[:`KNOWS`]->_1 create _0-[:`KNOWS`]->_2 start n=node(0) return n
Relationship by id
Binding a relationship as a starting point is done with the relationship(*)
function, which can also be abbreviated rel(*)
. See the section called “Node by id” for more information on Neo4j ids.
Query.
START r=relationship(0) RETURN r
The relationship with id 0
is returned.
Result
r |
---|
1 row |
|
Try this query live. create (_0 {`name`:"A"}) create (_1 {`name`:"B"}) create (_2 {`name`:"C"}) create _0-[:`KNOWS`]->_1 create _0-[:`KNOWS`]->_2 start r=relationship(0) return r
Multiple nodes by id
Multiple nodes are selected by listing them separated by commas.
Query.
START n=node(0, 1, 2) RETURN n
This returns the nodes listed in the START
statement.
Result
n |
---|
3 rows |
|
|
|
Try this query live. create (_0 {`name`:"A"}) create (_1 {`name`:"B"}) create (_2 {`name`:"C"}) create _0-[:`KNOWS`]->_1 create _0-[:`KNOWS`]->_2 start n=node(0, 1, 2) return n
Get multiple or all nodes
All nodes
To get all the nodes, use an asterisk. This can be done with relationships as well.
Tip The preferred way to do this is to use a |
Query.
START n=node(*) RETURN n
This query returns all the nodes in the graph.
Result
n |
---|
3 rows |
|
|
|
Try this query live. create (_0 {`name`:"A"}) create (_1 {`name`:"B"}) create (_2 {`name`:"C"}) create _0-[:`KNOWS`]->_1 create _0-[:`KNOWS`]->_2 start n=node(*) return n
Multiple starting points
Sometimes you want to bind multiple starting points. Just list them separated by commas.
Query.
START a=node(0), b=node(1) RETURN a,b
Both the nodes A
and the B
are returned.
Result
a | b |
---|---|
1 row | |
|
|
Try this query live. create (_0 {`name`:"A"}) create (_1 {`name`:"B"}) create (_2 {`name`:"C"}) create _0-[:`KNOWS`]->_1 create _0-[:`KNOWS`]->_2 start a=node(0), b=node(1) return a,b