查询花费了太多时间

Question

我想听听您对以下查询的看法：

select a.expense_code, a.expense_date, a.expense_supplier_code, b.supplier_name, a.expense_discount, a.expense_payment_method, a.expense_payment_transfer_to, a.expense_advance, a.expense_status,
                            sum(c.expense_item_buy_price * c.expense_item_quantity) , d.account_name, a.expense_counter, a.expense_type, a.expense_saving_type, a.expense_payment_transfer_from
                            from expense_data a, supplier_data b, expense_item c, tree_data d
                            where a.expense_supplier_code = b.supplier_code and a.expense_payment_transfer_to= d.account_code
                            and a.expense_counter = c.expense_counter
                            and a.expense_date between '2013-01-01' and '2014-01-01' and a.expense_status = 0 or a.expense_status = 2 group by (a.expense_counter);

即使在expense_data 表中有四个索引，此查询也花费了很多时间：

1- Expense_code. 
2- expense_user_id
3- expense_supplier_code
4- expense_payment_transfer_from

我不知道为什么要花这么多时间是因为两个太多的加入还是因为太多的indeces。你能建议吗？

Answer 1

重新编码以使连接更清晰（并删除如果费用状态是所有表都已连接的大量连接）给出：-

SELECT a.expense_code, 
    a.expense_date, 
    a.expense_supplier_code, 
    b.supplier_name, 
    a.expense_discount, 
    a.expense_payment_method, 
    a.expense_payment_transfer_to, 
    a.expense_advance, 
    a.expense_status,
    SUM(c.expense_item_buy_price * c.expense_item_quantity) , 
    d.account_name, 
    a.expense_counter, 
    a.expense_type, 
    a.expense_saving_type, 
    a.expense_payment_transfer_from
FROM expense_data a, 
INNER JOIN supplier_data b ON a.expense_supplier_code = b.supplier_code
INNER JOIN expense_item c ON a.expense_counter = c.expense_counter
INNER JOIN tree_data d ON a.expense_payment_transfer_to= d.account_code
WHERE a.expense_date BETWEEN '2013-01-01' AND '2014-01-01' 
AND a.expense_status = 0 OR a.expense_status = 2 
GROUP BY (a.expense_counter);

请注意，supper_data 表上的supplier_code 索引、expense_item 表上的expense_counter 索引和tree_data 表上account_code 的索引是很重要的。

我怀疑您真的不想退回费用状态为 0 且费用日期在该范围内的项目，无论日期如何，费用状态为 2 的任何记录都可能是您想要的：-

SELECT a.expense_code, 
    a.expense_date, 
    a.expense_supplier_code, 
    b.supplier_name, 
    a.expense_discount, 
    a.expense_payment_method, 
    a.expense_payment_transfer_to, 
    a.expense_advance, 
    a.expense_status,
    SUM(c.expense_item_buy_price * c.expense_item_quantity) , 
    d.account_name, 
    a.expense_counter, 
    a.expense_type, 
    a.expense_saving_type, 
    a.expense_payment_transfer_from
FROM expense_data a, 
INNER JOIN supplier_data b ON a.expense_supplier_code = b.supplier_code
INNER JOIN expense_item c ON a.expense_counter = c.expense_counter
INNER JOIN tree_data d ON a.expense_payment_transfer_to= d.account_code
WHERE a.expense_date BETWEEN '2013-01-01' AND '2014-01-01' 
AND a.expense_status IN (0, 2)
GROUP BY (a.expense_counter);

Answer 2

可能是您的 where 子句包含逻辑错误。 看最后一行（最后一个 OR 条件）：

where 
  ....
  and a.expense_counter = c.expense_counter 
  and a.expense_date BETWEEN '2013-01-01' AND '2014-01-01' 
  and a.expense_status = 0 
  or a.expense_status = 2 

这意味着“在日期等之间获取记录，并且状态为 0，或者获取所有状态为 2 的记录”

Answer 3

为了加快速度，您可能希望尝试在您加入的列的组合上创建组合索引。该索引可能比您现在拥有的四个独立索引更有用，尽管您仍然可以保留它们。除了这四个字段之外，您甚至可能想通过将status 和/或expense_data 添加到索引来进行试验。

Answer 4

您必须将 OR 条件放在括号中：

SELECT a.expense_code, 
   a.expense_date, 
   a.expense_supplier_code, 
   b.supplier_name, 
   a.expense_discount, 
   a.expense_payment_method, 
   a.expense_payment_transfer_to, 
   a.expense_advance, 
   a.expense_status, 
   SUM(c.expense_item_buy_price * c.expense_item_quantity), 
   d.account_name, 
   a.expense_counter, 
   a.expense_type, 
   a.expense_saving_type, 
   a.expense_payment_transfer_from 
FROM expense_data a, 
   supplier_data b, 
   expense_item c, 
   tree_data d 
WHERE a.expense_supplier_code = b.supplier_code 
   AND a.expense_payment_transfer_to = d.account_code 
   AND a.expense_counter = c.expense_counter 
   AND a.expense_date BETWEEN '2013-01-01' AND '2014-01-01' 
   AND (a.expense_status = 0 OR a.expense_status = 2)
GROUP BY a.expense_counter;