scql计算结果与MySQL的结果误差较大

[Rufus369]

我用相同的sql在scql和mysql执行，得到的结果误差挺大的，可以解释下原因嘛
scql：
SELECT ta.credit_rank, COUNT(*) as cnt, AVG(ta.income) as avg_income, AVG(tb.order_amount) as avg_amount FROM ta INNER JOIN tb ON ta.ID = tb.ID WHERE ta.age >= 20 AND ta.age <= 30 AND tb.is_active=1 GROUP BY ta.credit_rank;

[fetch]
2 rows in set: (324.059274ms)
+-------------+-----+-------------------+--------------------+
| credit_rank | cnt | avg_income | avg_amount |
+-------------+-----+-------------------+--------------------+
| 5 | 6 | 18069.77597427368 | 7743.3486404418945 |
| 6 | 4 | 336016.2181968689 | 5499.414562225342 |

mysql
SELECT alice.user_credit.credit_rank, COUNT(*) as cnt, AVG(alice.user_credit.income) as avg_income, AVG(bob.user_stats.order_amount) as avg_amount FROM alice.user_credit INNER JOIN bob.user_stats ON alice.user_credit.ID = bob.user_stats.ID WHERE alice.user_credit.age >= 20 AND alice.user_credit.age <= 30 AND bob.user_stats.is_active=1 GROUP BY alice.user_credit.credit_rank;

+-------------+-----+-------------+-------------------+
| credit_rank | cnt | avg_income | avg_amount |
+-------------+-----+-------------+-------------------+
| 6 | 4 | 336017.5000 | 5499.425048828125 |
| 5 | 6 | 18070.0000 | 7743.466796875 |
+-------------+-----+-------------+-------------------+
2 rows in set (0.00 sec)

[tongke6]

@Rufus369 从上面的执行结果来看，结果的绝对误差都很小（0.1~1.0左右之间），相对误差更小了～

MPC 计算是存在误差的，详情可见：https://www.secretflow.org.cn/docs/spu/latest/en-US/development/fxp

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