Orientdb SQL，从多个表中选择

Question

dont run "select from multiple tables" commands in orientdb 3.0 (centos)

i tested like this following commands

SELECT *
FROM Employee A, City B
WHERE A.city = B.id

Error Codes ; "Error parsing query: ^ Encountered " "SELECT "" at line 1, column 1. Was expecting one of: ... ... ";" ... DB name="

Answer 1

The most important difference between OrientDB and a Relational Database is that relationships are represented by LINKS instead of JOINs.

For this reason, the classic JOIN syntax is not supported. OrientDB uses the "dot (.) notation" to navigate LINKS. Example 1 : In SQL you might create a join such as:

SELECT *
FROM Employee A, City B
WHERE A.city = B.id
AND B.name = 'Rome'

In OrientDB an equivalent operation would be:

SELECT * FROM Employee WHERE city.name = 'Rome'

For more information: https://orientdb.com/docs/2.2.x/SQL.html#joins

Hope it helps

Regards