如果表2中有完整的ID列表，则可以使用该列表，但如果没有，则可以使用此列表：

SELECT ft.* 
FROM TABLE2 t2 RIGHT OUTER JOIN
(SELECT b.ID, a.ITEM_ID
  FROM TABLE1 a
    CROSS JOIN (SELECT DISTINCT ID FROM TABLE2) b) ft
      ON t2.id = ft.id AND t2.item_id = ft.item_id
WHERE t2.id IS NULL

http://sqlfiddle.com/#!9/2d0a19/7年
我做了一个 CROSS JOIN 获取所有可能组合的列表，然后从表中选择缺少的组合。

SELECT a.ID, b.item_id
FROM (SELECT DISTINCT ID FROM Table2) AS a 
-- or TableX AS a -- if you have a TableX with the unique ID values used for Table2 
CROSS JOIN Table1 AS b
-- or (SELECT DISTINCT item_id FROM Table2) AS b -- if Table1 was not available
LEFT JOIN Table2 AS c ON a.ID = c.ID AND b.item_id = c.item_id
WHERE c.ID IS NULL
;