Question

我有一个被定义为SELECT bellow的视图。有没有办法优化这个？现在它非常慢。

SELECT 
    -- lots of columns 
FROM   (((((((((((`table1` `t1`
                  LEFT JOIN `table2` `t2`
                    ON(( `t2`.`userid` = `t1`.`userid` )))
                 LEFT JOIN `table3` `t3`
                   ON(( `t1`.`orderid` = `t3`.`orderid` )))
                LEFT JOIN `table4` `t4`
                  ON(( `t4`.`orderitemlicenseid` =
                     `t3`.`orderitemlicenseid` )))
               LEFT JOIN `table5` `t5`
                 ON(( `t1`.`orderid` = `t5`.`orderid` )))
              LEFT JOIN `table6` `t6`
                ON(( `t5`.`transactionid` = `t6`.`transactionid` )))
             LEFT JOIN `table7` `t7`
               ON(( `t7`.`transactionid` = `t5`.`transactionid` )))
            LEFT JOIN `table8` `t8`
              ON(( `t8`.`voucherid` = `t7`.`voucherid` )))
           LEFT JOIN `table9` `t9`
             ON(( `t8`.`voucherid` = `t9`.`voucherid` )))
          LEFT JOIN `table10` `t10`
            ON(( ( `t10`.`vouchergroupid` = `t9`.`vouchergroupid` )
                 AND ( `t2`.`territoryid` = `t10`.`territoryid` ) )))
         LEFT JOIN `table11` `t11`
           ON(( `t11`.`voucherid` = `t8`.`voucherid` )))
        LEFT JOIN `table12` `t12`
          ON(( `t12`.`orderid` = `t1`.`orderid` )))
GROUP  BY `t5`.`transactionid`

EXPLAIN将返回如下内容：

id  select_type table   type    possible_keys   key key_len ref rows    Extra
1   PRIMARY <derived2>  ALL NULL    NULL    NULL    NULL    11571   
2   DERIVED t1  ALL NULL    NULL    NULL    NULL    11737   "Using temporary; Using filesort"
2   DERIVED t2  eq_ref  PRIMARY PRIMARY 4   database.o.userID   1   
2   DERIVED t3  ref fk_tblOrderItemLicenses_tblOrders1  fk_tblOrderItemLicenses_tblOrders1  4   database.o.orderID  1   
2   DERIVED t4  ref fk_tblOrderItemLicenseRefunds_tblOrderItemLicenses1 fk_tblOrderItemLicenseRefunds_tblOrderItemLicenses1 4   database.oil.orderItemLicenseID 1   "Using index"
2   DERIVED t5  ref fk_tblTransactions_tblOrders1   fk_tblTransactions_tblOrders1   4   database.o.orderID  1   
2   DERIVED t6  ref fk_tblTransactionCardDetails_tblTransactions1   fk_tblTransactionCardDetails_tblTransactions1   4   database.t.transactionID    1   
2   DERIVED t7  ref fk_tblVoucherTransactions_tblTransactions1  fk_tblVoucherTransactions_tblTransactions1  4   database.t.transactionID    1   
2   DERIVED t8  eq_ref  PRIMARY PRIMARY 4   database.vt.voucherID   1   
2   DERIVED t9  ref fk_tblVoucherVoucherGroups_tblVouchers1 fk_tblVoucherVoucherGroups_tblVouchers1 4   database.v.voucherID    1   "Using index"
2   DERIVED t10 eq_ref  PRIMARY PRIMARY 4   database.vvg.voucherGroupID 1   
2   DERIVED t11 ref fk_tblUserVouchers_tblVouchers  fk_tblUserVouchers_tblVouchers  4   database.v.voucherID    1   "Using index"
2   DERIVED t12 ref fk_tblTaiwanInvoiceData_tblOrders1  fk_tblTaiwanInvoiceData_tblOrders1  4   database.o.orderID  1

Answer 1

您可以创建一个“结果表”，在其中插入查询结果。您的项目从该结果表中读取其数据。然后创建一个作业（不确定mysql选项是什么），每小时/每周/每周运行慢查询以使结果表保持最新。

此外还有像索引一样的常见内容

如何使用这样的大量JOINS来优化SELECT查询？

1 个答案: