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[MySQL] all query tables contain 20million data -- how to optimize SQL

2022-06-28 05:46:00 【weixin_ forty-three million two hundred and twenty-four thousan】

This article sql How to optimize
All query tables have 2 Millions of data 

SELECT
	* 
FROM
	(
		( SELECT * FROM q_user_01 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_02 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_03 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_04 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_05 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_06 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_07 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_08 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_09 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) UNION ALL
		( SELECT * FROM q_user_10 WHERE id < 1162922 ORDER BY create_time DESC LIMIT 10 ) 
	) AS u 
WHERE
	u.id < 1162922 
ORDER BY
	u.create_time DESC 
	LIMIT 10

execution time :2.913s

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