Mysql View vs Query 性能

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

我的查询性能很慢，为了加快查询执行速度，我已经像这样修改了 MAIN_VIEW 由于 BASE_TABLE 已经在 MAIN_VIEW 上可用，我想从那时和那里获取 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

但是经过这个修改后，查询性能更差了..有人可以帮忙吗？我认为子视图不利于性能...

Answer 1

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