With the inclusion of java stored procedures in Neo4j 3.x, one can run Cypher to connect to a RDBMS using JDBC. To do so one needs to download and install https://github.com/neo4j-contrib/neo4j-apoc-procedures.
After installation of the Neo4j APOC kit, download the respective RDBMS JDBC driver .jar and install into $NEO4J_HOME\plugins\. The respective JDBC driver can be obtained from the RDBMS vendor. For example:
|Vendor||Download location||JDBC jar file|
After installing APOC and copying the RDBMS vendor .jar to $NEO4J_HOME\plugins\, restart Neo4j.
The apoc.load.jdbc stored procedure is used to connect over JDBC and takes 2 arguments,namely:
connection string SQL statement or table
The ‘connection string’ is vendor specific and as such one should consult the RDBMS vendor for syntax. The ‘SQL statement or table name’ could be for example ‘select * from movies’ or simply ‘movies’. Usage of a single table name would result in ‘select * from <table name>’
The following example would connect to a mysql database named proddb1 as user root with password=football and select all movies from the ‘movies’ table where the studio column was defined to be ‘MGM Studios’. Using this data we would then create nodes in Neo4j for all the movies meeting this criteria and define the title property.
If running the above results in error message similar to:
you may need to first manually load the driver by calling:
where ‘com.mysql.jdbc.Driver’ is the class name for the MySQL JDBC driver.
If you want to hide/alias the connection string, this can be accomplished by adding to the conf/neo4j.conf a parameter similar to:
and now the above Cypher can be rewritten as:
It should be noted that the
apoc.load.jdbc call is simply providing connectivity back to the RDBMS over JDBC.
The second argument can be any SQL statement, and that includes a SQL statement that may modify the source database through an UPDATE, DROP, TRUNCATE, etc.
If required, you might want to connect to the RDBMS with a user who only has SELECT privileges.
Also when loading data from JDBC, be mindful of datatypes and any necessary conversions; for example whereas MySQL supports a native DATE datatype, Neo4j does not. For example, to get the column with DATE data type, convert the value to a String when importing into Neo4j.