Der ON-Bedingungscode ist jeglicher Bedingungscode der Form, wie er auch in einer WHERE-Klausel benutzt werden kann.

SELECT t1.*, t2.* 
FROM t1 LEFT JOIN t2

SELECT 
    t1.*, t2.*, t3.* 
FROM 
    t1 LEFT JOIN t2 LEFT JOIN t3
ON t1.id= t2.id AND 
    t1.info = t3.info AND 
    t2.info2 = t3.info2 
WHERE 
    t1.datum > DATE_SUB(CURRENT_DATE, INTERVAL 1 DAY)
ORDER BY 
    t1.datum ASC

SELECT
*
FROM
  mod_nl_cronmanagement AS t1 LEFT JOIN
  mod_nl_groups AS t2 LEFT JOIN
  mod_nl_letters AS t3 
ON
  t1.PoolID = t2.nlgID AND t1.LetterID = t3.nllID
LIMIT 10

SELECT
*
FROM
  mod_nl_cronmanagement AS t1 JOIN
  mod_nl_groups AS t2 JOIN
  mod_nl_letters AS t3 
ON
  t1.PoolID = t2.nlgID AND t1.LetterID = t3.nllID
LIMIT 10

"SELECT var1, var2, var3 FROM tab1 LEFT JOIN tab2 ON id2=id1 LEFT JOIN tab3 ON id3=id1 WHERE ...."

SELECT a.feld1, a.feld2, ..., b.feld1, ..., c.feld1, c.feld2, ..., d.feld, ...
    FROM t1 a
    LEFT JOIN t2 b ON a.id = b.id
    LEFT JOIN t3 c ON a.id = c.id
    LEFT JOIN t3 d ON b.id = c.id
    WHERE a.datum > DATE_SUB(CURRENT_DATE, INTERVAL 1 DAY)
    ORDER BY a.datum ASC;