MySql 从一张表查询的数据赋值给另外一张表的字段（MySQL Update Query using a left join）

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举栗：
我们的用户积分出现重复数据，然后我们要把重复数据删除掉，重新计算用户总积分，假设所有积分都是增加的积分。

用户积分表test_user_points
用户iduser_id
用户积分总数point_count

积分记录表test_point_log
用户iduser_id
用户积分总数point

SQL：

UPDATE test_user_points AS a
LEFT JOIN (
	SELECT
		user_id,
		sum(point) AS point_count
	FROM
		test_point_log
	GROUP BY
		user_id
) AS b ON a.user_id = b.user_id
SET a.point_count = b.point_count

如果积分记录含有加减积分
积分记录表test_point_log
积分类型behavior_type，obtain为增加 consume为消耗

UPDATE sysuser_user_points_local_bak AS a
LEFT JOIN (
	SELECT
		user_id,
		sum(
			CASE
			WHEN behavior_type = 'obtain' THEN
				point
			ELSE
				0
			END
		) - sum(
			CASE
			WHEN behavior_type = 'consume' THEN
				point
			ELSE
				0
			END
		) AS point_count
	FROM
		sysuser_user_pointlog_online_bak_new
	GROUP BY
		user_id
) AS b ON a.user_id = b.user_id
SET a.point_count = b.point_count