为什么这个查询需要这么长时间才能执行
Why is this query taking so long to execute
我几个月前写了这个查询。 运行 很好。但是,这个查询的执行速度一天比一天慢。
除了相同的 table 执行之外,此查询还在多个 table 中检查帐单历史记录。
这里是查询-
SELECT * FROM (
SELECT *,
(SELECT username FROM users WHERE id = u_bills.UserId) AS username,
(SELECT first_name FROM users WHERE id = u_bills.UserId) AS first_name,
(SELECT last_name FROM users WHERE id = u_bills.UserId) AS last_name,
(SELECT phone FROM users WHERE id = u_bills.UserId) AS phone,
(SELECT email FROM users WHERE id = u_bills.UserId) AS email,
(SELECT CPRate FROM cpt WHERE UserId = u_bills.UserId ORDER BY AddedDate DESC LIMIT 0,1) AS cprate,
(SELECT (SELECT PopName FROM pops WHERE PopId = p.PopName) AS PopFullName FROM u_setupinfos AS p
WHERE UserId = u_bills.UserId) AS popname,
(SELECT active FROM users WHERE id = u_bills.UserId) AS active,
(SELECT SUM(PaidAmount) AS PaidAmount FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate)) AS PaidAmount,
(SELECT PaidDate FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate)
GROUP BY MONTH(PaidDate)) AS PaidDate,
(SELECT PaymentMedia FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate)
GROUP BY MONTH(PaidDate)) AS PaymentMedia,
(SELECT TransactionId FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate) GROUP BY MONTH(PaidDate)) AS TransactionId,
(SELECT GROUP_CONCAT(CONCAT(`BillHisId`,';',`PaidAmount`,';',`PaidDate`) separator '|') AS vals
FROM u_billhistory
WHERE UserId = u_bills.UserId
AND YEAR(PaidDate) = YEAR(CURDATE())) AS TotalPaids
FROM u_bills) AS m
WHERE m.username = 'abc'
请查看图片-
中的EXPLAIN
报告
我想组织这个查询。我需要建议让这个查询更快,比如 3 到 5 秒而不是 1 分半钟或更多。我在这个查询中犯了什么错误?
重要提示-
我几乎为查询中使用的每个列编制了索引
它很慢,因为您正在 运行 单独查找结果中每条记录的每个字段的附加 table...有时不止一个。您应该使用 JOIN 而不是嵌套的 SELECT。对于某些分组结果,您可以加入一个 SELECT
语句,该语句执行它自己的 GROUP BY。
此外,单独列上的单独索引不要帮助!!
将索引想象成一本 phone 书。一本简单的 phone 书籍在姓氏和名字上使用 聚集索引 。然后它还会列出每个项目的地址和 phone 编号。这就是聚簇索引:只是数据存储的顺序。
附加索引就像补充。 "Phone Number" 上的非聚集索引就像书末的补充,按顺序列出 phone 数字,然后显示姓氏和名字(但不显示地址)。 "Address" 上的索引会做同样的事情:一个单独的补充,按顺序列出地址,然后给你名字。
有了这些索引补充,如果你有一个phone号码,想知道地址,你必须先在补充中查找phone号码,才能找到名字,然后在主书中查找名称以获取地址。在这个例子中,phone 补充 确实有帮助 ,因为它比 phone 书的完整扫描更好。
但是,这里需要注意的重要一点是地址补充_does not 有助于此搜索,即使地址是您想要查找的确切字段。它可能对其他搜索有用,但在这种情况下没有帮助。此外,请记住,您的图书的每次更新不仅需要更新图书,还需要更新所有的增刊。不仅仅是存储space,而是更新每个索引所花费的时间。你需要考虑是否值得。如果您有一堆未使用的索引,那么最好不要使用它们。
回到您的具体问题,关于 唯一真正能帮助您的索引是 u_bills.username
、user.UserId
(希望它的集群是 table) u_billhistory.UserId
和 u_billhistory.PaidDate
.
的单个索引
这是重构此查询的初步尝试:
SELECT ub.*, u.username, u.first_name, u.last_name, u.phone, u.email, u.active,
m.PaidAmount, m.PaymentMedia, m.TransactionId,
y.TotalPaids, p.PopName As PopFullName, cpt2.CPRate
FROM u_bills ub
INNER JOIN users u on u.id = ub.UserId
INNER JOIN u_setupinfos usi on usi.UserId = ub.UserID
INNER JOIN pops p ON p.PopId = usi.PopName
INNER JOIN (
SELECT UserId, MIN(AddedDate) As cptDate
FROM cpt
GROUP BY UserID
) cpt1 ON cp1.UserID = ub.UserID
INNER JOIN (
SELECT UserID, AddedDate, MIN(CPRate) AS CPRate
FROM cpt
GROUP BY UserID, AddedDate
) cpt2 ON cpt2.UserID = ub.UserID AND cpt2.AddedDate = cpt1.ctpDate
INNER JOIN (
SELECT UserID, MONTH(PaidDate) PaidMonth, SUM(PaidAmount) AS PaidAmount,
PaymentMedia, TransactionId --these two fields need an aggregate function of some type!
FROM u_billhistory
GROUP BY UserId, MONTH(PaidDate)
) m ON m.UserID = ub.UserId AND m.PaidMonth = MONTH(ub.AddedDate)
INNER JOIN (
SELECT UserID, YEAR(PaidDate) As PaidYear,
GROUP_CONCAT(CONCAT(`BillHisId`,';',`PaidAmount`,';',`PaidDate`) separator '|') AS TotalPaids
FROM u_billhistory
WHERE YEAR(PaidDate) = YEAR(CurDate())
GROUP BY UserId, YEAR(PaidDate)
) y ON Y.UserId = ub.UserId
WHERE username='abc'
请注意,它并不十分完整,因为我们没有关于您的架构和数据的所有信息,而且似乎缺少一个 GROUP BY
和两个聚合函数。 MySql 这样不好...更好的数据库不会允许您查询 运行 直到您修复这些问题。
我几个月前写了这个查询。 运行 很好。但是,这个查询的执行速度一天比一天慢。
除了相同的 table 执行之外,此查询还在多个 table 中检查帐单历史记录。
这里是查询-
SELECT * FROM (
SELECT *,
(SELECT username FROM users WHERE id = u_bills.UserId) AS username,
(SELECT first_name FROM users WHERE id = u_bills.UserId) AS first_name,
(SELECT last_name FROM users WHERE id = u_bills.UserId) AS last_name,
(SELECT phone FROM users WHERE id = u_bills.UserId) AS phone,
(SELECT email FROM users WHERE id = u_bills.UserId) AS email,
(SELECT CPRate FROM cpt WHERE UserId = u_bills.UserId ORDER BY AddedDate DESC LIMIT 0,1) AS cprate,
(SELECT (SELECT PopName FROM pops WHERE PopId = p.PopName) AS PopFullName FROM u_setupinfos AS p
WHERE UserId = u_bills.UserId) AS popname,
(SELECT active FROM users WHERE id = u_bills.UserId) AS active,
(SELECT SUM(PaidAmount) AS PaidAmount FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate)) AS PaidAmount,
(SELECT PaidDate FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate)
GROUP BY MONTH(PaidDate)) AS PaidDate,
(SELECT PaymentMedia FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate)
GROUP BY MONTH(PaidDate)) AS PaymentMedia,
(SELECT TransactionId FROM u_billhistory
WHERE UserId = u_bills.UserId AND MONTH(AddedDate) = MONTH(PaidDate) GROUP BY MONTH(PaidDate)) AS TransactionId,
(SELECT GROUP_CONCAT(CONCAT(`BillHisId`,';',`PaidAmount`,';',`PaidDate`) separator '|') AS vals
FROM u_billhistory
WHERE UserId = u_bills.UserId
AND YEAR(PaidDate) = YEAR(CURDATE())) AS TotalPaids
FROM u_bills) AS m
WHERE m.username = 'abc'
请查看图片-
中的EXPLAIN
报告
我想组织这个查询。我需要建议让这个查询更快,比如 3 到 5 秒而不是 1 分半钟或更多。我在这个查询中犯了什么错误?
重要提示-
我几乎为查询中使用的每个列编制了索引
它很慢,因为您正在 运行 单独查找结果中每条记录的每个字段的附加 table...有时不止一个。您应该使用 JOIN 而不是嵌套的 SELECT。对于某些分组结果,您可以加入一个 SELECT
语句,该语句执行它自己的 GROUP BY。
此外,单独列上的单独索引不要帮助!!
将索引想象成一本 phone 书。一本简单的 phone 书籍在姓氏和名字上使用 聚集索引 。然后它还会列出每个项目的地址和 phone 编号。这就是聚簇索引:只是数据存储的顺序。
附加索引就像补充。 "Phone Number" 上的非聚集索引就像书末的补充,按顺序列出 phone 数字,然后显示姓氏和名字(但不显示地址)。 "Address" 上的索引会做同样的事情:一个单独的补充,按顺序列出地址,然后给你名字。
有了这些索引补充,如果你有一个phone号码,想知道地址,你必须先在补充中查找phone号码,才能找到名字,然后在主书中查找名称以获取地址。在这个例子中,phone 补充 确实有帮助 ,因为它比 phone 书的完整扫描更好。
但是,这里需要注意的重要一点是地址补充_does not 有助于此搜索,即使地址是您想要查找的确切字段。它可能对其他搜索有用,但在这种情况下没有帮助。此外,请记住,您的图书的每次更新不仅需要更新图书,还需要更新所有的增刊。不仅仅是存储space,而是更新每个索引所花费的时间。你需要考虑是否值得。如果您有一堆未使用的索引,那么最好不要使用它们。
回到您的具体问题,关于 唯一真正能帮助您的索引是 u_bills.username
、user.UserId
(希望它的集群是 table) u_billhistory.UserId
和 u_billhistory.PaidDate
.
这是重构此查询的初步尝试:
SELECT ub.*, u.username, u.first_name, u.last_name, u.phone, u.email, u.active,
m.PaidAmount, m.PaymentMedia, m.TransactionId,
y.TotalPaids, p.PopName As PopFullName, cpt2.CPRate
FROM u_bills ub
INNER JOIN users u on u.id = ub.UserId
INNER JOIN u_setupinfos usi on usi.UserId = ub.UserID
INNER JOIN pops p ON p.PopId = usi.PopName
INNER JOIN (
SELECT UserId, MIN(AddedDate) As cptDate
FROM cpt
GROUP BY UserID
) cpt1 ON cp1.UserID = ub.UserID
INNER JOIN (
SELECT UserID, AddedDate, MIN(CPRate) AS CPRate
FROM cpt
GROUP BY UserID, AddedDate
) cpt2 ON cpt2.UserID = ub.UserID AND cpt2.AddedDate = cpt1.ctpDate
INNER JOIN (
SELECT UserID, MONTH(PaidDate) PaidMonth, SUM(PaidAmount) AS PaidAmount,
PaymentMedia, TransactionId --these two fields need an aggregate function of some type!
FROM u_billhistory
GROUP BY UserId, MONTH(PaidDate)
) m ON m.UserID = ub.UserId AND m.PaidMonth = MONTH(ub.AddedDate)
INNER JOIN (
SELECT UserID, YEAR(PaidDate) As PaidYear,
GROUP_CONCAT(CONCAT(`BillHisId`,';',`PaidAmount`,';',`PaidDate`) separator '|') AS TotalPaids
FROM u_billhistory
WHERE YEAR(PaidDate) = YEAR(CurDate())
GROUP BY UserId, YEAR(PaidDate)
) y ON Y.UserId = ub.UserId
WHERE username='abc'
请注意,它并不十分完整,因为我们没有关于您的架构和数据的所有信息,而且似乎缺少一个 GROUP BY
和两个聚合函数。 MySql 这样不好...更好的数据库不会允许您查询 运行 直到您修复这些问题。