查询花费太多时间

Question

我想就以下查询提出您的想法：

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，此查询也会花费大量时间：

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次连接，还是因为过多的索引。 你能建议吗？

Answer 1

可能是您的where子句包含逻辑错误。 查看最后一行（last 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“获取日期之间的记录，等等，并且状态为0，或者获取状态为2的所有记录 ”

Answer 2

为了加快处理速度，您可能希望尝试对加入的列的组合进行合并索引。 该索引可能比您现在拥有的四个单独索引更有用，尽管您仍然可以保留它们。 除了这四个字段之外，您甚至还可以尝试通过将status和/或expense_data添加到索引来进行试验。

Answer 3

重新编码以使连接更清晰（并删除大规模连接，如果费用状态是所有表都被连接的话）：

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);

看到这一点很重要，您必须在Supplier_data表上的Supplier_code上有一个索引，在Expense_item表上的expense_counter上有一个索引，在tree_data表上的account_code上有一个索引。

我怀疑您真的不希望退回费用状态为0且费用日期在该范围内的项目，而无论费用日期如何，费用状态为2的任何记录，因此以下内容可能是您想要的：

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 4

您必须将OR条件放在方括号中：

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;