我正在开发一个跟踪用户当前位置并将其存储到SQLite数据库的应用程序。一切工作正常,但现在我有问题时查询数据库超过1000条记录的轨道,它需要近1.5分钟。在我的桌面上,它只需要1秒。为Android sqlite优化SQL语句
我知道这是一个查询与许多子选择,但我不能以另一种方式得到正确的结果。在我看来,这属于像avg()和sum()这样的集合函数。
这里是我的查询:
Cursor c = readableDB
.rawQuery(
"SELECT DISTINCT t._id , title , strftime('%Y-%m-%d' , starttime , 'unixepoch' , 'localtime') as date , description, "
+ "round((SELECT sum(distToPrev)/1000 FROM positions p WHERE p.trackid=t._id) , 2) as distance , "
+ "(SELECT count(latitude) FROM positions p WHERE p.trackid=t._id) as waypoints, "
+ "(SELECT (avg(speed)*3.6) FROM positions p WHERE p.trackid=t._id) as avgspeed, "
+ "(SELECT (max(speed)*3.6) FROM positions p WHERE p.trackid=t._id) as maxspeed, "
+ "(SELECT sum(altitudeUP) FROM positions p WHERE p.trackid=t._id) as climb , "
+ "(SELECT avg(heartbeat) FROM heartbeats h WHERE h.trackid=t._id) as avgheartbeat , "
+ "(SELECT max(heartbeat) FROM heartbeats h WHERE h.trackid=t._id) as maxheartbeat , "
+ "(SELECT avg(cadence) FROM heartbeats h WHERE h.trackid=t._id) as avgcadence "
+ "FROM tracks t LEFT JOIN heartbeats h ON t._id = h.trackid WHERE t._id = ?",
new String[]{String.valueOf(trackId)});
c.moveToFirst();
我怎样才能优化这个查询?我已经以这种方式尝试过了,但结果是错误的,花费了相同的时间。
SELECT t._id , title , strftime('%Y-%m-%d' , starttime , 'unixepoch' , 'localtime') as date , description,
sum(distToPrev)/1000 as distance ,
count(latitude) as waypoints,
(avg(speed)*3.6) as avgspeed,
(max(speed)*3.6) as maxspeed,
sum(altitudeUP) as climb ,
avg(heartbeat) as avgheartbeat ,
max(heartbeat) as maxheartbeat ,
avg(cadence) as avgcadence
FROM tracks t
LEFT JOIN heartbeats h ON t._id = h.trackid
INNER JOIN positions p ON t._id = p.trackid
WHERE t._id = ?
由于2个小时我正在寻找解决方案,我不知道我在做什么错。也许我必须休息一下。
编辑:
在这里,我创建语句:
CREATE TABLE heartbeats(_id INTEGER PRIMARY KEY AUTOINCREMENT, trackid INTEGER NOT NULL, heartbeat INTEGER NOT NULL, cadence INTEGER, timestamp TIMESTAMP);
CREATE TABLE positions(_id INTEGER PRIMARY KEY AUTOINCREMENT, trackid INTEGER NOT NULL, longitude REAL NOT NULL, latitude REAL NOT NULL, altitude REAL, altitudeUP REAL, speed REAL, accuracy REAL, distToPrev REAL, timestamp TIMESTAMP);
CREATE TABLE tracks(_id INTEGER PRIMARY KEY AUTOINCREMENT, title TEXT NOT NULL, description TEXT, starttime DATETIME NOT NULL, endtime DATETIME);
指定表别名,但无法将它们用于第一个SELECT列之外。我们不知道哪些表的剩余部分来自于能够建议任何有价值的东西...... – 2010-07-23 17:56:15
请张贴您的表架构,并包括您也有的索引。 – Pentium10 2010-07-23 17:57:19
添加了我的创建语句。表格中没有索引。 – tarantel 2010-07-23 18:23:06