Reviewing querying patterns

Let’s review a few query patterns and see how a database will try to execute them to understand how to write optimal queries:

• The following code segment shows one of the most common mistakes:

  MATCH (Mango {color: 'Yellow'}) return count(*)

We forgot to add :, even if Mango is a valid label. When we look at the query, we read it as return the count of yellow mangoes. Say we have mangoes, oranges, and apples in our cart. Since a database does not know what a mango is, it is going through all the fruits and checking for a color property, which should be Yellow, and returns the count of that. This is because when the database sees the query, it does not see the name Mango as a label.

Tip

Look for browser warnings before running the queries. Browsers are very good at highlighting these kinds of errors.

• The following code block is another common mistake made by developers:

  MATCH (p:Patient)--(e:Encounter) RETURN p,e

...