在 Neo4j 中导入具有空值的 CSV 文件

Question

This is supposed to be a really easy task and yet I am struggling. To all the people who are expert in a graph-database and Neo4j I would really appreciate some help and make my life a bit easier. I can't seem to figure out this MERGE clause with NULL values in CSV files.

Example.csv file contains

---

Name,Lastname,Team,Room

AAAA,BBBB,CCCC,1111

DDDD,EEEE,FFFF,2222

GGGG,HHHH,,3333

IIII,JJJJ,KKKK,

LLLL,MMMM,CCCC,1111

NNNN,OOOO,,2222

---

When executing

LOAD CSV WITH HEADERS FROM 'file:///EXAMPLE.csv' AS row WITH row RETURN row

I can see some fields like Team and Room has null values. I would like to create nodes for Employees, Team and Room and here is the code I have written so far.

---

CREATE CONSTRAINT ON (t:Team) ASSERT t.name IS UNIQUE;

CREATE CONSTRAINT ON (r:Room) ASSERT r.name IS UNIQUE;

LOAD CSV WITH HEADERS FROM 'file:///EXAMPLE.csv' AS row WITH row WHERE row.Room <> '' AND row.Room IS NOT NULL AND row.Team <> '' AND row.Team IS NOT NULL

CREATE (m:Employee {name: toUpper(row.Lastname), firstname: toUpper(row.Name)})

MERGE (r:Room { name:row.Room})

MERGE (t.Team {name:row.Team})

CREATE (m)-[:WORKS_IN]->(r)

CREATE (m)-[:WORKS_WITH]->(t);

---

I guess you already guessed some entries with null values are cancelled and not taken. I want to keep the Employees within the database even it has no entries in department or team ie. no relationship exists if null.

I would really appreciate some help and many thanks in advance.

Answer 1

You can try using FOREACH and CASE WHEN to handle conditions . Something like this:

CREATE (m:Employee {name: toUpper(row.Lastname), firstname: toUpper(row.Name)})
FOREACH (n IN (CASE WHEN row.Room IS NULL THEN [] ELSE [1] END) |
    MERGE (r:Room { name:row.Room})
    CREATE (m)-[:WORKS_IN]->(r)
)
FOREACH (n IN (CASE WHEN row.Team IS NULL THEN [] ELSE [1] END) |
    MERGE (t:Team {name:row.Team})
    CREATE (m)-[:WORKS_WITH]->(t)
)

The FOREACH block will be executed only once when the related line is different of null.