277 lines
14 KiB
Markdown
277 lines
14 KiB
Markdown
<!-- toc -->
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## 查询数据
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本教程将以Druid SQL和Druid的原生查询格式的示例演示如何在Apache Druid中查询数据。
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本教程假定您已经完成了摄取教程之一，因为我们将查询Wikipedia编辑样例数据。
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* [加载本地文件](./chapter-1.md)
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* [从Kafka加载数据](./chapter-2.md)
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* [从Hadoop加载数据](./chapter-3.md)
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Druid查询通过HTTP发送,Druid控制台包括一个视图，用于向Druid发出查询并很好地格式化结果。
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### Druid SQL查询
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Druid支持SQL查询。
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该查询检索了2015年9月12日被编辑最多的10个维基百科页面
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```
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SELECT page, COUNT(*) AS Edits
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FROM wikipedia
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WHERE TIMESTAMP '2015-09-12 00:00:00' <= "__time" AND "__time" < TIMESTAMP '2015-09-13 00:00:00'
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GROUP BY page
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ORDER BY Edits DESC
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LIMIT 10
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```
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让我们来看几种不同的查询方法
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#### 通过控制台查询SQL
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您可以通过在控制台中进行上述查询：
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控制台查询视图通过内联文档提供自动补全功能。
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您还可以从 `...` 选项菜单中配置要与查询一起发送的其他上下文标志。
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请注意，控制台将（默认情况下）使用带Limit的SQL查询，以便可以完成诸如`SELECT * FROM wikipedia`之类的查询,您可以通过 `Smart query limit` 切换关闭此行为。
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查询视图提供了可以为您编写和修改查询的上下文操作。
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#### 通过dsql查询SQL
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为方便起见，Druid软件包中包括了一个SQL命令行客户端，位于Druid根目录中的 `bin/dsql`
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运行 `bin/dsql`, 可以看到如下：
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```
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Welcome to dsql, the command-line client for Druid SQL.
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Type "\h" for help.
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dsql>
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```
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将SQl粘贴到 `dsql` 中提交查询：
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```
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dsql> SELECT page, COUNT(*) AS Edits FROM wikipedia WHERE "__time" BETWEEN TIMESTAMP '2015-09-12 00:00:00' AND TIMESTAMP '2015-09-13 00:00:00' GROUP BY page ORDER BY Edits DESC LIMIT 10;
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┌──────────────────────────────────────────────────────────┬───────┐
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│ page │ Edits │
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├──────────────────────────────────────────────────────────┼───────┤
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│ Wikipedia:Vandalismusmeldung │ 33 │
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│ User:Cyde/List of candidates for speedy deletion/Subpage │ 28 │
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│ Jeremy Corbyn │ 27 │
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│ Wikipedia:Administrators' noticeboard/Incidents │ 21 │
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│ Flavia Pennetta │ 20 │
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│ Total Drama Presents: The Ridonculous Race │ 18 │
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│ User talk:Dudeperson176123 │ 18 │
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│ Wikipédia:Le Bistro/12 septembre 2015 │ 18 │
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│ Wikipedia:In the news/Candidates │ 17 │
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│ Wikipedia:Requests for page protection │ 17 │
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└──────────────────────────────────────────────────────────┴───────┘
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Retrieved 10 rows in 0.06s.
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```
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#### 通过HTTP查询SQL
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SQL查询作为JSON通过HTTP提交
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教程包括一个示例文件, 该文件`quickstart/tutorial/wikipedia-top-pages-sql.json`包含上面显示的SQL查询, 我们将该查询提交给Druid Broker。
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```
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curl -X 'POST' -H 'Content-Type:application/json' -d @quickstart/tutorial/wikipedia-top-pages-sql.json http://localhost:8888/druid/v2/sql
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```
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结果返回如下：
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```
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[
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{
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"page": "Wikipedia:Vandalismusmeldung",
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"Edits": 33
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},
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{
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"page": "User:Cyde/List of candidates for speedy deletion/Subpage",
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"Edits": 28
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},
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{
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"page": "Jeremy Corbyn",
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"Edits": 27
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},
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{
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"page": "Wikipedia:Administrators' noticeboard/Incidents",
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"Edits": 21
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},
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{
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"page": "Flavia Pennetta",
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"Edits": 20
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},
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{
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"page": "Total Drama Presents: The Ridonculous Race",
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"Edits": 18
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},
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{
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"page": "User talk:Dudeperson176123",
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"Edits": 18
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},
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{
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"page": "Wikipédia:Le Bistro/12 septembre 2015",
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"Edits": 18
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},
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{
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"page": "Wikipedia:In the news/Candidates",
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"Edits": 17
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},
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{
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"page": "Wikipedia:Requests for page protection",
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"Edits": 17
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}
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]
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```
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#### 更多Druid SQL示例
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这是一组可尝试的查询:
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**时间查询**
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```
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SELECT FLOOR(__time to HOUR) AS HourTime, SUM(deleted) AS LinesDeleted
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FROM wikipedia WHERE "__time" BETWEEN TIMESTAMP '2015-09-12 00:00:00' AND TIMESTAMP '2015-09-13 00:00:00'
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GROUP BY 1
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```
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**聚合查询**
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```
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SELECT channel, page, SUM(added)
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FROM wikipedia WHERE "__time" BETWEEN TIMESTAMP '2015-09-12 00:00:00' AND TIMESTAMP '2015-09-13 00:00:00'
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GROUP BY channel, page
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ORDER BY SUM(added) DESC
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```
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**查询原始数据**
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```
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SELECT user, page
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FROM wikipedia WHERE "__time" BETWEEN TIMESTAMP '2015-09-12 02:00:00' AND TIMESTAMP '2015-09-12 03:00:00'
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LIMIT 5
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```
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#### SQL查询计划
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Druid SQL能够解释给定查询的查询计划, 在控制台中，可以通过 `...` 按钮访问此功能。
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如果您以其他方式查询，则可以通过在Druid SQL查询之前添加 `EXPLAIN PLAN FOR` 来获得查询计划。
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使用上边的一个示例：
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`EXPLAIN PLAN FOR SELECT page, COUNT(*) AS Edits FROM wikipedia WHERE "__time" BETWEEN TIMESTAMP '2015-09-12 00:00:00' AND TIMESTAMP '2015-09-13 00:00:00' GROUP BY page ORDER BY Edits DESC LIMIT 10;`
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```
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dsql> EXPLAIN PLAN FOR SELECT page, COUNT(*) AS Edits FROM wikipedia WHERE "__time" BETWEEN TIMESTAMP '2015-09-12 00:00:00' AND TIMESTAMP '2015-09-13 00:00:00' GROUP BY page ORDER BY Edits DESC LIMIT 10;
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┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ PLAN │
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├─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
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│ DruidQueryRel(query=[{"queryType":"topN","dataSource":{"type":"table","name":"wikipedia"},"virtualColumns":[],"dimension":{"type":"default","dimension":"page","outputName":"d0","outputType":"STRING"},"metric":{"type":"numeric","metric":"a0"},"threshold":10,"intervals":{"type":"intervals","intervals":["2015-09-12T00:00:00.000Z/2015-09-13T00:00:00.001Z"]},"filter":null,"granularity":{"type":"all"},"aggregations":[{"type":"count","name":"a0"}],"postAggregations":[],"context":{},"descending":false}], signature=[{d0:STRING, a0:LONG}]) │
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└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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Retrieved 1 row in 0.03s.
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```
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### 原生JSON查询
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Druid的原生查询格式以JSON表示。
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#### 通过控制台原生查询
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您可以从控制台的"Query"视图发出原生Druid查询。
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这是一个查询，可检索2015-09-12上具有最多页面编辑量的10个wikipedia页面。
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```
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{
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"queryType" : "topN",
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"dataSource" : "wikipedia",
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"intervals" : ["2015-09-12/2015-09-13"],
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"granularity" : "all",
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"dimension" : "page",
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"metric" : "count",
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"threshold" : 10,
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"aggregations" : [
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{
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"type" : "count",
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"name" : "count"
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}
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]
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}
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```
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只需将其粘贴到控制台即可将编辑器切换到JSON模式。
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#### 通过HTTP原生查询
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我们在 `quickstart/tutorial/wikipedia-top-pages.json` 文件中包括了一个示例原生TopN查询。
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提交该查询到Druid：
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```
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curl -X 'POST' -H 'Content-Type:application/json' -d @quickstart/tutorial/wikipedia-top-pages.json http://localhost:8888/druid/v2?pretty
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```
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您可以看到如下的查询结果：
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```
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[ {
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"timestamp" : "2015-09-12T00:46:58.771Z",
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"result" : [ {
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"count" : 33,
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"page" : "Wikipedia:Vandalismusmeldung"
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}, {
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"count" : 28,
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"page" : "User:Cyde/List of candidates for speedy deletion/Subpage"
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}, {
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"count" : 27,
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"page" : "Jeremy Corbyn"
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}, {
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"count" : 21,
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"page" : "Wikipedia:Administrators' noticeboard/Incidents"
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}, {
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"count" : 20,
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"page" : "Flavia Pennetta"
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}, {
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"count" : 18,
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"page" : "Total Drama Presents: The Ridonculous Race"
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}, {
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"count" : 18,
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"page" : "User talk:Dudeperson176123"
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}, {
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"count" : 18,
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"page" : "Wikipédia:Le Bistro/12 septembre 2015"
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}, {
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"count" : 17,
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"page" : "Wikipedia:In the news/Candidates"
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}, {
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"count" : 17,
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"page" : "Wikipedia:Requests for page protection"
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} ]
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} ]
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```
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### 进一步阅读
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[查询文档]()有更多关于Druid原生JSON查询的信息
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[Druid SQL文档]()有更多关于Druid SQL查询的信息 |