Over a million developers have joined DZone.
{{announcement.body}}
{{announcement.title}}

Neo4j & Cypher: Parameterized Queries and neo4j-shell

DZone's Guide to

Neo4j & Cypher: Parameterized Queries and neo4j-shell

· Java Zone ·
Free Resource

Verify, standardize, and correct the Big 4 + more– name, email, phone and global addresses – try our Data Quality APIs now at Melissa Developer Portal!

Every now and then I get sent Neo4j cypher queries to look at, and more often than not they’re parameterised, which means you can’t easily run them in the Neo4j browser.

For example let’s say we have a database which has a user called ‘Mark’:

CREATE (u:User {name: "Mark"})

Now we write a query to find ‘Mark’ with the name parametrized so we can easily search for a different user in future:

MATCH (u:User {name: {name}}) RETURN u

If we run that query in the Neo4j browser we’ll get this error:

Expected a parameter named name
Neo.ClientError.Statement.ParameterMissing

If we try that in neo4j-shell we’ll get the same exception to start with:

$ MATCH (u:User {name: {name}}) RETURN u;
ParameterNotFoundException: Expected a parameter named name

However, as Michael pointed out to me, the neat thing about neo4j-shell is that we can define parameters by using the export command:

$ export name="Mark"
$ MATCH (u:User {name: {name}}) RETURN u;
+-------------------------+
| u                       |
+-------------------------+
| Node[1923]{name:"Mark"} |
+-------------------------+
1 row

export is a bit sensitive to spaces so it’s best to keep them to a minimum. e.g. the following tries to create the variable ‘name ‘ which is invalid:

$ export name = "Mark"
name  is no valid variable name. May only contain alphanumeric characters and underscores.

The variables we create in the shell don’t have to only be primitives. We can create maps too:

$ export params={ name: "Mark" }
$ MATCH (u:User {name: {params}.name}) RETURN u;
+-------------------------+
| u                       |
+-------------------------+
| Node[1923]{name:"Mark"} |
+-------------------------+
1 row

A simple tip but one that saves me from having to rewrite queries all the time!

Developers! Quickly and easily gain access to the tools and information you need! Explore, test and combine our data quality APIs at Melissa Developer Portal – home to tools that save time and boost revenue. Our APIs verify, standardize, and correct the Big 4 + more – name, email, phone and global addresses – to ensure accurate delivery, prevent blacklisting and identify risks in real-time.

Topics:

Published at DZone with permission of

Opinions expressed by DZone contributors are their own.

{{ parent.title || parent.header.title}}

{{ parent.tldr }}

{{ parent.urlSource.name }}