CODEWITHSUNDEEP
neo4jcyphergraph-databases
degath
degath

Reputation: 1621

Cypher Conditional `ORDER BY` clause (same property, differ ASC/DESC)

I have two queries:

MATCH (n:Node) 
RETURN n.value
ORDER BY n.value DESC
LIMIT 5

MATCH (n:Node) 
RETURN n.value
ORDER BY n.value ASC
LIMIT 5

I would like to combine them both by adding an additional parameter. I tried different approaches with CASE statement, but it looks like the CASE statement allows me to change the property of the sort, not the type of the sort...

This is a pseudo-code that does what I'm trying to achieve (But this one obviously doesn't work):

WITH "ASC" AS sortType
MATCH (n:Node) 
RETURN n.value
ORDER BY n.value (CASE WHEN sortType = "ASC" THEN ASC ELSE DESC END)
LIMIT 5

So the final question is:

Upvotes: 0

Views: 211

Answers (2)

Ksenia
Ksenia

Reputation: 1

You can add 2 expressions for ORDER BY:

     CASE WHEN sortType = "ASC" THEN n.value ELSE null END ASC,
     CASE WHEN sortType = "ASC" THEN null ELSE n.value END DESC

They will be both applied, but the first one won't do anything when sortType is not "ASC" and the second won't do anything when the sortType is "ASC".

Upvotes: 0

Graphileon
Graphileon

Reputation: 5385

You can add a column with a sortValue like this

RETURN  n.value,
        CASE WHEN sortType = ‘DESC’ THEN n.value * -1 ELSE n.value END AS sortValue
ORDER BY sortValue

Adding the sortValue in your RETURN statement makes that you get either

| value | sortValue |
|     1 |          1|
|     2 |          2|
|     3 |          3|

OR

| value | sortValue |
|     3 |         -3|
|     2 |         -2|
|     1 |         -1|

You can use this mechanism also in case you want to have flexibility with regard to which column you want to sort, as long as you make sure that you put the right value in the sortValue column.

Upvotes: 1

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