mysql 多表查詢數據重複的問題

廢話不多說直接貼SQL語句

SELECT
	moments.id AS id,
	COUNT(endorse.id) AS endorseCount,
	COUNT(reply.id) AS replyCount
FROM
	jq_circle_moments moments
LEFT JOIN jq_circle_endorse endorse ON moments.id = endorse.moments_id
LEFT JOIN jq_circle_reply reply ON moments.id = reply.moments_id
WHERE
	moments.`status` = "10B"
AND moments.id = "090bf03723fd4abba56dfecfa69ac410"
GROUP BY
	moments.id
LIMIT 10

結果是：

id	endorseCount	replyCount
090bf03723fd4abba56dfecfa69ac410	9	9

然後我在執行

select COUNT(id) FROM jq_circle_endorse where moments_id = "090bf03723fd4abba56dfecfa69ac410";

select COUNT(id) FROM jq_circle_reply where moments_id = "090bf03723fd4abba56dfecfa69ac410";

分別結果是：

COUNT(id)

3

COUNT(id)

3

然後我就納悶了，爲什麼應該是9應該是3，後面靈機一動加了個去重的關鍵字DISTINCT

SELECT
	moments.id AS id,
	COUNT(DISTINCT endorse.id) AS endorseCount,
	COUNT(DISTINCT reply.id) AS replyCount
FROM
	jq_circle_moments moments
LEFT JOIN jq_circle_endorse endorse ON moments.id = endorse.moments_id
LEFT JOIN jq_circle_reply reply ON moments.id = reply.moments_id
WHERE
	moments.`status` = "10B"
AND moments.id = "090bf03723fd4abba56dfecfa69ac410"
GROUP BY
	moments.id
LIMIT 10

自從有了mybatis-plus SQL語句都寫的少了