Question

我正在使用多个OUTER APPLY进行查询，但所有表都在已连接的列上具有主键（因此这里使用了聚簇索引），因此我不知道如何进一步优化此查询。此处也无法使用索引视图，因为禁止使用ORDER BY和TOP。

所以我有

表Fields包含Id主键和各种其他列。
WeatherHistory表包含复杂的主键（FieldId和[Date]）以及许多列，
NdviImageHistory表格FieldId，[Date]，[Base64]列（复杂主键FieldId和[Date]）其中{{ 1}}存储图像base64，
[Base64]表格NaturalColorImageHistory，FieldId，[Date]列（复杂主键[Base64]和FieldId）其中{{ 1}}存储图像base64，
[Date]表包含[Base64]，NdviHistory，FieldId列（复杂主键[Date]和MeanNdvi），< / p>
FieldId表包含[Date]，FieldSeasonHistory，Field列（复杂主键StartDate和EndDate）。

我的查询

FieldId

我还没有创建任何索引，因为我认为自动生成的clusted索引（基于主键）应该足够（但我可能是错的）。此查询执行大约15秒，但我想减少查询时间。

修改：为[Date]表的SELECT Fields.*, WeatherHistory.TempSumC AS CurrentTempSumC, TempSumF AS CurrentTempSumF, PrecipitationSumMm AS CurrentPrecipitationSumMm, nih.[Base64] AS CurrentNdviImageBase64, ncih.[Base64] AS CurrentNaturalColorImageBase64, MeanNdvi AS CurrentMeanNdvi, IsOpenSeason FROM Fields LEFT JOIN WeatherHistory ON FieldId = Id AND [Date] = CAST(GETUTCDATE() AS DATE) OUTER APPLY ( SELECT TOP 1 [Base64] FROM NdviImageHistory WHERE FieldId = Id ORDER BY [Date] DESC ) nih OUTER APPLY ( SELECT TOP 1 [Base64] FROM NaturalColorImageHistory WHERE FieldId = Id ORDER BY [Date] DESC ) ncih OUTER APPLY ( SELECT TOP 1 MeanNdvi FROM NdviHistory WHERE FieldId = Id ORDER BY [Date] DESC ) nh OUTER APPLY ( SELECT TOP 1 CASE WHEN EndDate IS NULL THEN 1 ELSE 0 END AS IsOpenSeason FROM FieldSeasonHistory WHERE FieldId = Id ORDER BY [StartDate] DESC ) fsh WHERE UserId = (SELECT Id FROM Users WHERE Email = @email) AND IsArchived = 0和UserId列添加了索引。查询执行计划：

**编辑2：**统计：

IsArchived

Answer 1

您需要为每个表提供多列索引。索引应该是order by中的列，列select中的列，然后是NdviImageHistory(FieldId, [Date], [Base64])中的列。例如：

NaturalColorImageHistory(FieldId, [Date], [Base64])
export default class LineChartPresentational extends React.Component { constructor(props) { super(); this.state = { isclicked: true, }} changeStrokeclick() { this.setState({isclicked: !this.state.isclicked} )} render() { let strokecolor = this.state.isclicked ? "#9da0a5" : "#2d75ed" return ( <div> <div id="lclastdataref" style={{ textAlign: 'right' }}> <span>Last Data Refresh: {linechartdf.date} </span> </div> <div className='line-charts'> <div className="line-chart-wrapper " style={{ width: window.innerWidth / 2, height: window.innerHeight / 2, }}> <ResponsiveContainer> <LineChart width={width} height={height} margin={{ top: 20, right: 20, bottom: 20, left: 20 }} data={linechartdata} id="Line-Chart"> <XAxis dataKey={xAxisColumn} /> <YAxis domain={['auto', 'auto']} /> <Tooltip cursor={false} /> { linechartdata.map((entry, index) => ( <Line stroke={strokecolor} onClick={this.changeStrokeclick.bind(this)} name={linechartdata[index].dataKey} strokeWidth={lineThickness} dataKey={`value${index + 1}`} dot={false} className={`value${index + 1}`}/> )) } </LineChart> </ResponsiveContainer> </div> </div> </div> ); }
等等。

Answer 2

像这样更新您的查询。

SELECT Fields.*,
    WeatherHistory.TempSumC AS CurrentTempSumC,
    TempSumF AS CurrentTempSumF,
    PrecipitationSumMm AS CurrentPrecipitationSumMm,
    nih.[Base64] AS CurrentNdviImageBase64,
    ncih.[Base64] AS CurrentNaturalColorImageBase64,
    MeanNdvi AS CurrentMeanNdvi,
    IsOpenSeason
FROM Fields
LEFT JOIN WeatherHistory ON FieldId = Id AND [Date] = CAST(GETUTCDATE() AS DATE)
OUTER APPLY
(
    SELECT MAX(NdviImageHistory.ID) MAX_ID
    FROM NdviImageHistory
    WHERE FieldId = Id

) nih_ID
OUTER APPLY
(
    SELECT [Base64] FROM NdviImageHistory X WHERE X.ID = nih_ID.MAX_ID
)nih

用户更多外部申请所有这些表{nih，ncih，nh，fsh} 试试这个。

我只使用1个外部[nih]

从OUTER APPLY Joins中删除TOP 1和Order by

使用多个OUTER APPLY优化查询

2 个答案: