mysql百万数据关联查询优化

Question

问题遇到的现象和发生背景

book表有上百万条数据，查询时间长，请问如何只通过修改sql语句，优化查询

问题相关代码，请勿粘贴截图

SELECT
a.name,
s.score,
b.sex,
c.age,
e.price
FROM
book a
LEFT JOIN milk s ON a.Id = s.id
LEFT JOIN fruit b ON a.Id = b.id
LEFT JOIN water c ON a.num= c.id
LEFT JOIN apple e ON a.num2 = e.id

Answer 1

如果不建立索引的话不管是a表放在左边还是b表放在左边都是一样效果，可以给a表建立一个索引，这样效率可以大大提高，可以参考我的下面的文章
https://blog.csdn.net/weixin_44096133/article/details/123373462?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165867491816781818717607%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=165867491816781818717607&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_ecpm_v1~rank_v31_ecpm-1-123373462-null-null.185^v2^control&utm_term=mysql&spm=1018.2226.3001.4450