Question

以下查询不断超时，是否有更少的开销方式来实现相同的功能？

UPDATE Invoices SET ispaid = 0 
WHERE Invoice_number IN (SELECT invoice_number
    FROM payment_allocation
    WHERE transactionID=305)

我正在做的是从一个事务中取消分配发票，最多可以返回30多条记录但是每当我尝试运行它时它就会停止数据库死亡

Answer 1

使用加入而不是子查询，它将提高性能。

如果您尚未创建，请在两个表格中的 Invoice_number 列上创建索引。

试试这个：

UPDATE Invoices i 
INNER JOIN payment_allocation pa ON i.Invoice_number = pa.invoice_number 
SET i.ispaid = 0 
WHERE pa.transactionID = 305;

Answer 2

我会尝试EXISTS：

UPDATE Invoices a set ispaid=0 
WHERE EXISTS 
(
 SELECT NULL FROM payment_allocation b 
 WHERE b.Invoice_number =a.Invoice_number AND b.transactionID=305
)

Answer 3

从MySQL 5.5开始，无法优化子查询选择（查询中的另一个完整选择语句）。这可能是您的查询速度太慢的原因。重构您查询以摆脱内部select语句。

 UPDATE Invoices, payment_allocation
  SET ispaid=0 
  WHERE payment_allocation.transactionID=305 AND       
        Invoices.Invoice_number = payment_allocation.invoice_number

一个有趣的旁注......但MariaDB（由原始创建者创建的MySQL分支）已经实现了Subquery选择优化。

Answer 4

UPDATE invoices i
  JOIN payment_allocation pa
    ON pa.invoice_number = i.invoice_number
   SET i.ispaid=0 
 WHERE pa.transactionID = 305;

MYSQL嵌套查询运行速度很慢？

4 个答案: