连接两个没有公共列的表

Question

I want to join two tables together combing two fields in table 1 to form composite keys and combining two fields in table 2 to form composite keys.

The primary keys will be dropped because tables get truncated in ETL

CREATE TABLE collection]
(
    collectionid INT NOT NULL PRIMARY KEY,
    spaceid INT NOT NULL,
    collectionpa VARCHAR(150) NOT NULL,
    collectionto VARCHAR (150) NOT NULL
)

CREATE TABLE objects
(
    birstobj INT NOT NULL PRIMARY KEY
    birstspace INT NOT NULL,
    collectionid INT NOT NULL,
    object_nm VARCHAR(150) NOT NULL,
    object_label VARCHAR (150)NOT NULL
)

composite keys in table 1 spaceid and collectionpa composite keys in table 2 birstspace and collectionid

Answer 1

A join condition is just like any other SQL condition - you can use both the columns there:

SELECT *
FROM   collection c
JOIN   object o ON c.collectionid = o.collectionid AND
                   c.spaceid = o.birstspace