Working with subqueries

Cypher allows you to write subqueries using the CALL clause. There are two types of subqueries available:

• Returning subqueries
• Unit subqueries

The subqueries are evaluated for each incoming row that is provided by the parent query.

Let us work with returning subqueries first.

Working with returning subqueries

Subqueries that end with a RETURN statement are called returning subqueries. Every row from a returning subquery is combined with the input row to prepare the result of the query. This means the final output of the outer query can be impacted by the subquery returned values.

Note

If a subquery does not return any rows, then there will not be any rows returned by the outer query.

Returning subqueries are very useful when we want to apply sorting and extra filtering to UNION queries. When we use the UNION clause, it is not possible to apply any sorting. Let us take a look at a UNION query with sorting using a subquery...