Filter, Aggregate, and Combine Results

The UNION statement

Suppose we want to know how many books and how many authors are stored in our database. We can perform two queries to get these values, but with the UNION statement, we can merge these data together. Just put the UNION keyword between two or more queries, as shown in the following query:

MATCH (b:Book)
RETURN 'Books' as type, COUNT(b) as cnt
UNION ALL
MATCH (a:Person)
RETURN 'Authors' as type, COUNT(a) as cnt

The result is as follows:

+-----------------+
| type      | cnt |
+-----------------+
| "Books"   | 150 |
| "Authors" | 142 |
+-----------------+

The only condition we must be careful of with the UNION statement is that the result set must have the same number of columns and the columns must have the same names.

You're perhaps wondering why we used the UNION ALL statement and not the UNION statement in the previous example. There is a subtle difference between them—the UNION statement removes duplicated rows after merging results, so it is slower.

Tip

If you don't care...

Tech Concepts

Programming languages

Tech Tools

Unlimited access to the largest independent learning library in tech of over 8,000 expert-authored tech books and videos.

Innovative learning tools, including AI book assistants, code context explainers, and text-to-speech.

50+ new titles added per month and exclusive early access to books as they are being written.

Learning Cypher

By : Onofrio Panzarino

Learning Cypher

By: Onofrio Panzarino

Overview of this book

The UNION statement

Tip

Learning Cypher

By : Onofrio Panzarino

Learning Cypher

By: Onofrio Panzarino

Overview of this book

The UNION statement

Tip

Confirmation

Buy this book with your credits?

Submit Your Feedback

Create a Free Account To Continue Reading

Sign in to activate your 7-day free access