Case Expression

CASE is used for conditional expression. There are two variants of conditional expression in Cypher. A simple form which compares an expression against multiple expressions and a general form with multiple conditional statements.

Simple Form

In the simple form, input is compared against each WHEN in order until a match is found. If no match is found, the expression in the ELSE is returned. If there is no ELSE, NULL is returned.

Syntax

CASE input
    WHEN expr THEN result
    [WHEN ...]
    [ELSE expr]
END

Example

MATCH (a:User) RETURN 
    CASE a.age 
        WHEN 50 THEN a.name 
    END AS x;

Output:

---------
| x     |
---------
|       |
---------
|       |
---------
| Zhang |
---------
|       |
---------

View example in Colab.

General Form

In the general form, conditional statements are evaluated in order until a true statement is found. If no match is found, the expression in the ELSE is returned. If there is no ELSE, NULL is returned.

Syntax

CASE
    WHEN expr THEN result
    [WHEN ...]
    [ELSE expr]
END

Example

MATCH (a:User) RETURN 
    CASE
        WHEN a.age < 50 THEN a.name 
    ELSE 'dummy'
    END AS x;

Ouput:

-----------
| x       |
-----------
| Adam    |
-----------
| Karissa |
-----------
| dummy   |
-----------
| Noura   |
-----------

View example in Colab.