[英]How can I make this MySQL SELECT + GROUP BY query more efficient?
[英]How can I make select query more efficient using inner join
我想从多个表中选择数据,但随着数据变大,我的系统在从 MySQL 数据库中获取时变得很慢。
我怎样才能使这个查询更有效。
SELECT s.id,s.regiNo,
s.firstName as fname,
s.middleName as mname,
s.lastName as lname,
s.gender, s.class_group, c.subjects,
e.mid_term, e.count_assessment, e.examid,
e.scored, e.internaltype, e.Class,
e.Year,e.total_score,e.sub_highest,e.sub_lowest,
e.first_term,e.second_term,e.third_term,e.avg_score
FROM student s
inner join exam e on s.regiNo = e.Roll_Number
inner join subjects c on e.sub_id = c.subect_code
group by s.regiNo, s.firstName, s.middleName, s.lastName,
s.gender, s.class_group, c.subjects,
e.mid_term, e.count_assessment, e.examid, e.scored, e.internaltype,
e.Class, e.Year,e.total_score,e.sub_highest,e.sub_lowest,
e.first_term,e.second_term,e.third_term,e.avg_score,s.id
我看到您有 ID 列,如果那是您的 PK,那么您可能需要一些索引。
尝试在 JOINING 列上创建索引.. 例如 regiNo、Roll_Number
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