谢谢你的澄清。这就简单了一点。我将把第二年的数据放在子查询中，过滤第一年的主表，数量=0。这将给你两个专栏，一个是第一年，一个是第二年。如果您只查找单个产品标识的此信息，则需要将此信息添加到这两个标识中 WHERE 条款。

SELECT TABLE_NAME.ACCOUNT_ID, TABLE_NAME.QUANTITY AS "2019" , YEAR_TWO.QUANTITY AS "2020"
FROM TABLE_NAME
LEFT JOIN 
          (
            SELECT *
            FROM TABLE 
            WHERE YEAR = 2020
          ) YEAR_TWO ON TABLE_NAME.ACCOUNT_ID = YEAR_TWO.ACCOUNT_ID
WHERE TABLE_NAME.YEAR = 2019
AND TABLE_NAME.QUANTITY = 0

如果你只想要第二年不再是0的帐户的百分比，你可以尝试这样的方法（把所有的1加起来，除以总数）

SELECT TABLE_NAME.YEAR,  SUM(YEAR_TWO.QUANTITY) / COUNT(YEAR_TWO.QUANTITY) AS PERCENTAGE_NOT_ZERO
FROM TABLE_NAME
LEFT JOIN 
          (
            SELECT *
            FROM TABLE 
            WHERE YEAR = 2020
          ) YEAR_TWO ON TABLE_NAME.ACCOUNT_ID = YEAR_TWO.ACCOUNT_ID
WHERE TABLE_NAME.YEAR = 2019
AND TABLE_NAME.QUANTITY = 0
GROUP BY TABLE_NAME.YEAR