mysql分组排序后加序号

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    根据产品品类编号分组后按照产品安全指数排序，并加序号。

SELECT
	id,
	product_classify_id,
	p_coefficient,
	rank
FROM
	(
		SELECT
			*,@rownum :=@rownum + 1 AS rownum,

		IF (
			@pa = ff.product_classify_id ,@rank :=@rank + 1 ,@rank := 1
		) AS rank ,@pa := ff.product_classify_id
		FROM
			(
				SELECT
					id,
					product_classify_id,
					p_coefficient
				FROM
					jp_product
				WHERE
					enabled = 1
				GROUP BY
					product_classify_id,
					id
				ORDER BY
					CAST(
						product_classify_id AS signed
					) ASC,
					CAST(
						p_coefficient AS DECIMAL (3, 2)
					) DESC
			) ff,
			(
				SELECT
					@rank := 0 ,@rownum := 0 ,@pa = NULL
			) tt
	) result

id：产品编号，product_classify_id：产品品类编号，p_coefficient：产品安全指数，rank：序号。

CAST用于将字符串转为数字。

查询结果如下：