问如何仅使用内部联接创建左联接？

EN

CREATE TABLE #testusers (userid INT)

CREATE TABLE #testusers2 (userID INT)

INSERT INTO #testusers (userid)
VALUES (1)
    , (2)
    , (3)

INSERT INTO #testusers2 (userid)
VALUES (2), (5), (1)


--Expecting to see one result due to straight inner join
SELECT t1.*
    , t2.*
FROM #testusers t1
INNER JOIN #testusers2 t2
    ON t1.userid = t2.userid

--Forcing all results by basically doing a cross apply and then NULLing out non matching values based on the join condition
SELECT distinct t1.*
    , MAX(CASE 
        WHEN t1.userid <> t2.userID
            THEN NULL
        ELSE t2.userid
        END) AS userid
FROM #testusers t1
INNER JOIN #testusers2 t2
    ON t1.userid = t2.userid
        OR 1 = 1
GROUP BY t1.userid

CREATE TABLE #testusersnames (username varchar(10))

CREATE TABLE #testusersnames2 (username varchar(10))

INSERT INTO #testusersnames (username)
VALUES ('Tom')
    , ('Jane')
    , ('Dick')

INSERT INTO #testusersnames2 (username)
VALUES ('Tom'), ('Sally'), ('Mary')

SELECT t1.*
    , t2.*
FROM #testusersnames t1
INNER JOIN #testusersnames2 t2
    ON t1.username = t2.username

--Forcing all results by basically doing a cross apply and then NULLing out non matching values based on the join condition
SELECT distinct t1.*
    , MAX(CASE 
        WHEN t1.username <> t2.username
            THEN NULL
        ELSE t2.username
        END) AS username
FROM #testusersnames t1
INNER JOIN #testusersnames2 t2
    ON t1.username = t2.username
        OR 1 = 1
GROUP BY t1.username

CREATE TABLE demo (id int, name varchar(32));

CREATE TABLE demo_details (demo_id int, description varchar(64));

INSERT INTO demo_details
VALUES (1,
        'Woohooooooooo');

SELECT *
FROM demo d
INNER JOIN demo_details dd ON d.id = dd.demo_id
UNION
SELECT d.*,
       NULL,
       NULL
FROM demo d
INNER JOIN demo_details dd ON d.id <> dd.demo_id;

SELECT * 
FROM Table1 t1
INNER JOIN (
  SELECT * FROM Table2
  UNION 
  SELECT {NULL for every column in Table2}
) t2
  ON 1=1
WHERE t1.id = t2.id
OR t2.id IS NULL