如何加快这个查询？

Question

ATM我正在努力学习如何有效地使用数据库知识,并希望获得一些专家意见.我目前没有任何性能问题.我想知道,你将如何使用此查询处理索引:

SELECT B.event, 
       COALESCE(B.system, C.surname || ' ' || C.forename) AS name, 
       C.label, 
       B.timestamp
FROM A            
  INNER JOIN B ON A.event=B.event
  INNER JOIN C ON B.state=C.id
  LEFT OUTER JOIN D ON B.hur=D.id             
WHERE A.id IN(12,13,14,15,...) 
  ORDER BY B.event, B.timestamp

A.id,C.id并且D.id已经是主键

UPDATE 通常我会把INDEX(A.event)和INDEX(B.event,B.timestamp)放在一起.它是否正确？那么B.event,B.state和B.hur呢？

Answer 1

将您的查询重写为：

SELECT  B.event, 
        COALESCE(B.system, C.surname || ' ' || C.forename) AS name, 
        C.label, 
        B.timestamp
FROM    B            
INNER JOIN
        C
ON      C.id = B.state
LEFT OUTER JOIN
        D
ON      D.id = B.hur
WHERE   B.event IN
        (
        SELECT  event
        FROM    A
        WHERE   A.id IN (12, 13, 14, 15)
        )
ORDER BY
        B.event, B.timestamp

，并创建复合索引B (event, timestamp)