我有两个关系表。从他们那里，我想计算出一个SELECT查询，该查询检索列中“介于”值之间的项目。
我是MySQL的新手，这种查询并不是我的强项。我确定我是从错误的角度看问题。希望我能从这里站稳脚跟！
好吧，这行：我有两个表： products 和 line_items ，其中 product_id 是第一个的主键，带有一个与后者中的匹配字段有很多关系。这些表包含以下列：
产品
product_id
line_items
product_id
timestamp_out
timestamp_in
时间戳记指示何时已从库存中取出产品，何时又将其重新插入库存中。相同的 product_id 可以在 line_items 中出现多次，并且 timestamp_out 总是小于 timestamp_in 。
我想做的是在未“签出”产品时检索 product_id 。
例如 product_id 1，可能在 line_items 中包含以下行：
第一行
-timestamp_out: 1
-timestamp_in: 3
第二行
-timestamp_out: 6
-timestamp_in: 7
我想要实现的是一个查询，该查询将使用两个任意时间戳，并返回在两个时间戳之间未检出的产品（例如，查询中的时间戳是否为：4和6：那么不应返回product_id 1，因为该范围的上限频谱与第二行的时间跨度交叉；仅当查询中的时间戳超出：4和in：5或更高时7应该返回 product_id 1）。
我尝试了几种查询变体，但我想是“最接近”的一种：
SELECT
products.product_id
FROM
products
INNER JOIN
line_items
ON
(products.product_id = line_items.product_id)
WHERE
6 NOT BETWEEN line_items.timestamp_out AND timestamp_in
OR
4 NOT BETWEEN line_items.timestamp_out AND timestamp_in
这不起作用，因为它返回 product_id 1，看看第一行的条件如何。如果我将其反转为：
WHERE
6 BETWEEN line_items.timestamp_out AND timestamp_in
OR
4 BETWEEN line_items.timestamp_out AND timestamp_in
...这当然也会返回 product_id 1，因为查询的跨度与第二行的跨度交叉。
希望我能解决问题！我必须承认，在过去的几个小时中，我对此感到有些不安，而又无法全神贯注于如何进行这类MySQL查询！
答案 0 :(得分：0)
这是一个适合您的用例的查询。
public class AudioProcessor {
private Context context;
private FFmpeg ffmpeg;
private AudioProcessorListener listener;
private File micPcmFile;
private File backgroundMp3File;
private File pcmtowavTempFile;
private File mp3towavTempFile;
private File combinedwavTempFile;
private File outputFile;
private File volumeChangedTempFile;
private FFtask currentTask;
private int videoRecordingLength = 0;
TextView extensionDownload, percentProgress;
private static final String TAG = "FFMPEG AV Processor";
public AudioProcessor(Context context, Activity activity) {
ffmpeg = null;
ffmpeg = FFmpeg.getInstance(context);
percentProgress = activity.findViewById(R.id.percentProgress);
percentProgress.setSingleLine(false);
this.context = context;
prepare();
}
/**
* Program main method. Starts running program
* @throws Exception
*/
public void process() throws Exception {
if (!ffmpeg.isSupported()) {
Log.e(TAG, "FFMPEG not supported! Cannot convert audio!");
throw new RuntimeException("FFMPeg has to be supported");
}
if (!checkIfAllFilesPresent()) {
Log.e(TAG, "All files are not set yet. Please set file first");
throw new RuntimeException("Files are not set!");
}
Log.e(TAG, "Start processing audio!");
listener.onStart();
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
@Override
public void run() {
convertPCMToWav();
}
}, 200);
}
/**
* Prepares program
*/
private void prepare() {
Log.d(TAG, "Preparing everything...");
prepareTempFiles();
}
/**
* Converts PCM to wav file. Automatically create new file.
*/
private void convertPCMToWav() {
Log.d(TAG, "Convert PCM TO Wav");
//ffmpeg -f s16le -ar 44.1k -ac 2 -i file.pcm file.wav
String[] cmd = { "-f" , "s16le", "-ar", "44.1k", "-i", micPcmFile.toString(), "-y", pcmtowavTempFile.toString()};
currentTask = ffmpeg.execute(cmd, new ExecuteBinaryResponseHandler() {
@Override
public void onStart() {
super.onStart();
percentProgress.setVisibility(View.VISIBLE);
percentProgress.setText("Converting your recording\n"+"1/5");
}
@Override
public void onSuccess(String message) {
super.onSuccess(message);
convertMP3ToWav();
}
@Override
public void onFailure(String message) {
super.onFailure(message);
onError(message);
convertPCMToWav();
}
});
}
/**
* Converts mp3 file to wav file.
* Automatically creates Wav file
*/
private void convertMP3ToWav() {
Log.e(TAG, "Convert MP3 TO Wav");
//ffmpeg -ss 0 -t 30 -i file.mp3 file.wav
//String[] cmd = { "-ss", "0", "-t", Integer.toString(videoRecordingLength), "-i" , backgroundMp3File.toString(), "-y", mp3towavTempFile.toString() };
String[] cmd = { "-i" , backgroundMp3File.toString(), "-y", mp3towavTempFile.toString() };
currentTask = ffmpeg.execute(cmd, new ExecuteBinaryResponseHandler() {
@Override
public void onStart() {
super.onStart();
percentProgress.setText("Converting background audio\n"+"2/5");
Log.d(TAG, "Convert MP3 TO Wav");
}
@Override
public void onSuccess(String message) {
super.onSuccess(message);
changeMicAudio();
}
@Override
public void onFailure(String message) {
super.onFailure(message);
Log.e(TAG, "Failed to convert MP3 TO Wav");
onError(message);
throw new RuntimeException("Failed to convert MP3 TO Wav");
}
});
}
/**
* Combines 2 wav files into one wav file. Overlays audio
*/
private void combineWavs() {
Log.e(TAG, "Combine wavs");
//ffmpeg -i C:\Users\VR1\Desktop\_mp3.wav -i C:\Users\VR1\Desktop\_pcm.wav -filter_complex amix=inputs=2:duration=first:dropout_transition=3 C:\Users\VR1\Desktop\out.wav
String[] cmd = { "-i" , pcmtowavTempFile.toString(), "-i", volumeChangedTempFile.toString(), "-filter_complex", "amix=inputs=2:duration=first:dropout_transition=3", "-y",combinedwavTempFile.toString()};
currentTask = ffmpeg.execute(cmd, new ExecuteBinaryResponseHandler() {
@Override
public void onStart() {
super.onStart();
percentProgress.setText("Combining the two audio files\n"+"4/5");
}
@Override
public void onSuccess(String message) {
super.onSuccess(message);
encodeWavToAAC();
}
@Override
public void onFailure(String message) {
super.onFailure(message);
onError(message);
}
});
}
private void changeMicAudio(){
Log.e(TAG, "Change audio volume");
//ffmpeg -i input.wav -filter:a "volume=1.5" output.wav
String[] cmdy = { "-i", mp3towavTempFile.toString(), "-af", "volume=0.9", "-y",volumeChangedTempFile.toString()};
currentTask = ffmpeg.execute(cmdy, new ExecuteBinaryResponseHandler() {
@Override
public void onStart() {
super.onStart();
percentProgress.setText("Normalizing volume\n"+"3/5");
}
@Override
public void onSuccess(String message) {
combineWavs();
super.onSuccess(message);
}
@Override
public void onFailure(String message) {
super.onFailure(message);
Log.e("AudioProcessor", message);
}
});
}
/**
* Do something on error. Releases program data (deletes files)
* @param message
*/
private void onError(String message) {
completed();
if (listener != null) {
//listener.onError(message);
}
}
/**
* Encode to AAC
*/
private void encodeWavToAAC() {
Log.d(TAG, "Encode Wav file to AAC");
//ffmpeg -i file.wav -c:a aac -b:a 128k -f adts output.m4a
String[] cmd = { "-i" , combinedwavTempFile.toString(), "-c:a", "aac", "-b:a", "128k", "-f", "adts", "-y",outputFile.toString()};
currentTask = ffmpeg.execute(cmd, new ExecuteBinaryResponseHandler() {
@Override
public void onStart() {
super.onStart();
percentProgress.setText("Normalizing volume\n"+"3/5");
}
@Override
public void onSuccess(String message) {
super.onSuccess(message);
if (listener != null) {
listener.onSuccess(outputFile);
}
completed();
}
@Override
public void onFailure(String message) {
super.onFailure(message);
onError(message);
encodeWavToAAC();
}
});
}
/**
* Uninitializes class
*/
private void completed() {
if (listener != null) {
listener.onFinish();
}
Log.d(TAG, "Process completed successfully!");
destroyTempFiles();
}
/**
* Prepares temp required files by deleteing them if they exsist.
* Files cannot exists before ffmpeg actions. FFMpeg automatically creates those files.
*/
private void prepareTempFiles() {
Log.d(TAG, "Preparing Temp files...");
pcmtowavTempFile = new File(context.getFilesDir()+ Common.TEMP_LOCAL_DIR + "/" + "_pcm.wav");
mp3towavTempFile = new File(context.getFilesDir()+ Common.TEMP_LOCAL_DIR + "/" + "_mp3.wav");
combinedwavTempFile = new File(context.getFilesDir()+ Common.TEMP_LOCAL_DIR + "/" + "_combined.wav");
volumeChangedTempFile = new File(context.getFilesDir()+ Common.TEMP_LOCAL_DIR + "/" + "_volumeChanged.wav");
}
/**
* Destroys temp required files
*/
private void destroyTempFiles() {
Log.d(TAG, "Destroying Temp files...");
pcmtowavTempFile.delete();
mp3towavTempFile.delete();
combinedwavTempFile.delete();
volumeChangedTempFile.delete();
Log.d(TAG, "Destroying files completed!");
}
/**
* Checks if all files are set, so we can process them
* @return - all files ready
*/
private boolean checkIfAllFilesPresent() {
if(micPcmFile == null || backgroundMp3File == null || outputFile == null) {
Log.e(TAG, "All files are not set! Set all files!");
throw new RuntimeException("Output file is not present!");
}
Log.d(TAG, "All files are present!");
return true;
}
public void setOutputFile(File outputFile) {
this.outputFile = outputFile;
}
public void setListener(AudioProcessorListener listener) {
this.listener = listener;
}
public void setMicPcmFile(File micPcmFile) {
this.micPcmFile = micPcmFile;
}
public void setBackgroundMp3File(File backgroundMp3File) {
this.backgroundMp3File = backgroundMp3File;
}
public void setVideoRecordingLength(int seconds) {
this.videoRecordingLength = seconds;
}
/**
* Quits current processing ffmpeg task
*/
public void killCurrentTask() {
if (currentTask != null) {
currentTask.killRunningProcess();
}
}
public interface AudioProcessorListener {
void onStart();
void onSuccess(File output);
void onError(String message);
void onFinish();
}
}
对于每种产品，查询确保select p.*
from products p
where not exists (
select 1
from line_items l
where
l.product_id = p.product_id
AND NOT (
l.timestamp_in < @out
OR l.timestamp_out > @in
)
);
中没有记录与给定间隔重叠。
我用您的示例数据 in this db fiddle 进行了测试，它似乎与您的预期结果相符，即：
line_items：没有结果@out=4, @in=6：选择了产品1 @out=4, @in=5：选择了产品1 答案 1 :(得分：0)
让我们调用定义您要查询query_start和query_end的范围的时间戳。
如果line_items（查询范围在产品缺货前结束）或query_end < timestamp_out行中的时间戳范围不与查询范围重叠query_start > timestamp_in（在产品退货后开始查询范围）。
我们正在寻找一种产品，其中该产品的所有line_item行均不与范围重叠-或者，不存在不重叠的行。
select *
from product p
where not exists (
select *
from line_items i
where i.product_id = p.product_id
and not (@query_end < i.timestamp_out or @query_start > i.timestamp_in)
)