Window 在 android 的 SQLite 中运行
Window functions in android's SQLite
我正在努力 android 尝试使用 window 函数。我有一个数据库，其中有一个 created_at 字段和一个测试字段的条目，当我尝试使用该代码为每个测试获取创建的最大值时（我的代码在 Kotlin 中，但我猜 java 代码是一样的）
db.rawQuery("SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;", arrayOf()).close()
我的应用程序崩溃了，但是有那个代码
db.rawQuery("SELECT MAX(created_at) FROM test_result;", arrayOf()).close()
一切正常
显然在那个用例中，我可以做一个子查询并加入最大值的 table，但实际上我想要做的需要获取每个条目的最后 4 个条目的平均值测试，所以我真的需要 window 函数，我很困惑它们在 android 中不起作用，因为它们在普通 SQLite
中起作用
还有，报错完全没用
09-03 07:58:28.627 10723 10723 E AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.memorizer/com.example.memorizer.TestActivity}: android.database.sqlite.SQLiteException: near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Error Code : 1 (SQLITE_ERROR)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Caused By : SQL(query) error or missing database.
09-03 07:58:28.627 10723 10723 E AndroidRuntime: (near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2957)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.-wrap11(Unknown Source:0)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:105)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.os.Looper.loop(Looper.java:164)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:6944)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Caused by: android.database.sqlite.SQLiteException: near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Error Code : 1 (SQLITE_ERROR)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Caused By : SQL(query) error or missing database.
09-03 07:58:28.627 10723 10723 E AndroidRuntime: (near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:1096)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:661)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:59)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1746)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1685)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.example.memorizer.TestActivity.getData(TestActivity.kt:202)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.example.memorizer.TestActivity.onCreate(TestActivity.kt:184)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.Activity.performCreate(Activity.java:7183)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2910)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: ... 9 more
我的sqlite版本是3.18.2
感谢您的宝贵时间
编辑：问题是我 phone 上的 sqlite 版本，3.25.0 是第一个引入 window 函数的版本，而我的版本比那个版本更旧
Window 函数是在 SQLite 3.25 中添加的，而你是 运行 版本 3.18。
what I am trying to do requires getting the mean value over the last 4 entries for each test,
另一种方法是相关子查询：
SELECT
created_at,
(
SELECT AVG(value)
FROM test_result t1
WHERE t1.test = t.test and t1.created_at <= t.created_at
ORDER BY t1.created_at DESC LIMIT 4
) running_avg_value
FROM test_result t
这将为您提供当前行和同一测试的最后 3 条记录的 运行 平均值，按 created_at 排序。
为了提高性能，请考虑 (test, created_at, value) 上的索引。即便如此，这可能无法很好地适应大型数据集。如果您要升级到最新版本（应该真正考虑），您可以将子查询替换为：
AVG(value) OVER(PARTITION BY test ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)
我正在努力 android 尝试使用 window 函数。我有一个数据库，其中有一个 created_at 字段和一个测试字段的条目，当我尝试使用该代码为每个测试获取创建的最大值时（我的代码在 Kotlin 中，但我猜 java 代码是一样的）
db.rawQuery("SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;", arrayOf()).close()
我的应用程序崩溃了，但是有那个代码
db.rawQuery("SELECT MAX(created_at) FROM test_result;", arrayOf()).close()
一切正常
显然在那个用例中，我可以做一个子查询并加入最大值的 table，但实际上我想要做的需要获取每个条目的最后 4 个条目的平均值测试，所以我真的需要 window 函数，我很困惑它们在 android 中不起作用，因为它们在普通 SQLite
中起作用还有，报错完全没用
09-03 07:58:28.627 10723 10723 E AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.memorizer/com.example.memorizer.TestActivity}: android.database.sqlite.SQLiteException: near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Error Code : 1 (SQLITE_ERROR)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Caused By : SQL(query) error or missing database.
09-03 07:58:28.627 10723 10723 E AndroidRuntime: (near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2957)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3032)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.-wrap11(Unknown Source:0)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1696)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.os.Handler.dispatchMessage(Handler.java:105)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.os.Looper.loop(Looper.java:164)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:6944)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at java.lang.reflect.Method.invoke(Native Method)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:327)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1374)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Caused by: android.database.sqlite.SQLiteException: near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Error Code : 1 (SQLITE_ERROR)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: Caused By : SQL(query) error or missing database.
09-03 07:58:28.627 10723 10723 E AndroidRuntime: (near "(": syntax error (code 1): , while compiling: SELECT MAX(created_at) OVER (PARTITION BY test ORDER BY created_at) FROM test_result;)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: #################################################################
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:1096)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:661)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:59)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1746)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1685)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.example.memorizer.TestActivity.getData(TestActivity.kt:202)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at com.example.memorizer.TestActivity.onCreate(TestActivity.kt:184)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.Activity.performCreate(Activity.java:7183)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1220)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2910)
09-03 07:58:28.627 10723 10723 E AndroidRuntime: ... 9 more
我的sqlite版本是3.18.2
感谢您的宝贵时间
编辑：问题是我 phone 上的 sqlite 版本，3.25.0 是第一个引入 window 函数的版本，而我的版本比那个版本更旧
Window 函数是在 SQLite 3.25 中添加的，而你是 运行 版本 3.18。
what I am trying to do requires getting the mean value over the last 4 entries for each test,
另一种方法是相关子查询：
SELECT
created_at,
(
SELECT AVG(value)
FROM test_result t1
WHERE t1.test = t.test and t1.created_at <= t.created_at
ORDER BY t1.created_at DESC LIMIT 4
) running_avg_value
FROM test_result t
这将为您提供当前行和同一测试的最后 3 条记录的 运行 平均值，按 created_at 排序。
为了提高性能，请考虑 (test, created_at, value) 上的索引。即便如此，这可能无法很好地适应大型数据集。如果您要升级到最新版本（应该真正考虑），您可以将子查询替换为：
AVG(value) OVER(PARTITION BY test ROWS BETWEEN 3 PRECEDING AND CURRENT ROW)