Question

我有一个基本查询，它使用一个使用另一个视图的视图，就像这样。

SELECT a,b,c,DEBIT_AMOUNT, CREDIT_AMOUNT FROM MAIN_VIEW WHERE a='foo' AND c='bar';

这是架构

create table BASE_TABLE (
id int not null auto_increment,
a varchar(20),
b varchar(20),
c varchar(20),
primary key (id));

create table OTHER_TABLE (
oid int not null auto_increment,
id int not null,
mtype varchar(10),
amount varchar(20),
primary key (oid));

create or replace  view `MAIN_VIEW` AS 
SELECT  BT.a, BT.b, BT.c,SUB_VIEW.DEBIT_AMOUNT, SUB_VIEW.CREDIT_AMOUNT
    FROM  BASE_TABLE BT
    LEFT JOIN  SUB_VIEW  ON SUB_VIEW.id = BT.id

create or replace  view `SUB_VIEW` AS 
SELECT  BT.id, 
      ( SELECT  SUM(O.amount)
            FROM  OTHER_TABLE O
            WHERE  O.mtype = 'DR'
              AND  O.id = BT.id 
      ) AS DEBIT_AMOUNT, 
      ( SELECT  SUM(O.amount)
            FROM  OTHER_TABLE O
            WHERE  O.mtype = 'CR'
              AND  O.id = BT.id 
      ) AS CREDIT_AMOUNT
    FROM  BASE_TABLE BT

我的查询是性能非常慢，为了加快查询执行速度，我修改了MAIN_VIEW就像这样由于BASE_TABLE已经在MAIN_VIEW上可用，我想从那时起取得DEBIT_AMOUNT和CREDIT_AMOUNT而不是进入SUB_VIEW

- MAIN_VIEW ---

create or replace  view `MAIN_VIEW` AS 
SELECT  BT.a, BT.b, BT.c, 
      ( SELECT  SUM(O.amount)
            FROM  OTHER_TABLE O
            WHERE  O.mtype = 'DR'
              AND  O.id = BT.id 
      ) AS DEBIT_AMOUNT, 
      ( SELECT  SUM(O.amount)
            FROM  OTHER_TABLE O
            WHERE  O.mtype = 'CR'
              AND  O.id = BT.id 
      ) AS CREDIT_AMOUNT
    FROM  BASE_TABLE BT

但经过这次修改后，查询性能更差..任何人都可以帮忙吗？我认为子视图对性能不利......

Answer 1

您需要INDEX(id, mtype)（按任意顺序）。这应该使子查询更快，因此整个查询更快。

Mysql View vs Query性能

1 个答案: