怎么新建MySQL数据库

发布时间：2021-05-15 作者：admin
阅读：575

我们在使用MongoDB查询时，模糊查询是比较常见用和实用，因此大家要掌握MongoDB模糊查询操作。为了让大家对MongoDB模糊查询有更深的认识，这篇文章就给大家介绍一下关于MongoDB模糊查询的操作，下面就跟随小编一起来看看吧。

1.作用与语法描述

作用：正则表达式是使用指定字符串来描述、匹配一系列符合某个句法规则的字符串。许多程序设计语言都支持利用正则表达式进行字符串操作。MongoDB 使用 $regex 操作符来设置匹配字符串的正则表达式。

语法一

{ <field>: { $regex: /pattern/, $options: '<options>' } }
{ <field>: { $regex: 'pattern', $options: '<options>' } }
{ <field>: { $regex: /pattern/<options> } }

语法二

{ <field>: /pattern/<options> }

2.案例演示

假设MongoDB中存放了我们OrderService服务的消息信息，其数据如下：

（以下为演示所用到的9个文档）

{
  "_id" : ObjectId("5d305b1c4857fc49c0c14c81"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b3b4857fc49c0c14c82"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b404857fc49c0c14c83"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b454857fc49c0c14c84"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b4b4857fc49c0c14c85"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b4f4857fc49c0c14c86"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305bb74857fc49c0c14c87"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"shenzheng\\\" origincode=\\\"QQ0003\\\" />

  </Body></Response>\""
},
{
  "_id" : ObjectId("5d305bd14857fc49c0c14c88"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"zhongshan\\\" origincode=\\\"QQ0002\\\" />

  </Body></Response>\""
},
{
  "_id" : ObjectId("5d305be94857fc49c0c14c89"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"zhongshan\\\" origincode=\\\"QQ0001\\\" />

  </Body></Response>\""
}

需求：查询 data 字段含有字符 <Head>OK</Head>的文档

执行代码如下：

db.dbtestregex.find({data:{ $regex:/<Head>OK<\/Head>/}})

查询代码中的 \ 为转移符，以下查询语句也是如此。

返回结果如下：

{
  "_id" : ObjectId("5d305bb74857fc49c0c14c87"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"shenzheng\\\" origincode=\\\"QQ0003\\\" />

  </Body></Response>\""
},
{
  "_id" : ObjectId("5d305bd14857fc49c0c14c88"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"zhongshan\\\" origincode=\\\"QQ0002\\\" />

  </Body></Response>\""
},
{
  "_id" : ObjectId("5d305be94857fc49c0c14c89"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"zhongshan\\\" origincode=\\\"QQ0001\\\" />

  </Body></Response>\""
}

上面的查询命令也可以改写成：

db.dbtestregex.find({data:/<Head>OK<\/Head>/})

其查询结果是一样的，如下：

{
  "_id" : ObjectId("5d305bb74857fc49c0c14c87"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"shenzheng\\\" origincode=\\\"QQ0003\\\" />

  </Body></Response>\""
},
{
  "_id" : ObjectId("5d305bd14857fc49c0c14c88"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"zhongshan\\\" origincode=\\\"QQ0002\\\" />

  </Body></Response>\""
},
{
  "_id" : ObjectId("5d305be94857fc49c0c14c89"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>OK</Head><Body><OrderResponse filter_mmm=\\\"2\\\" destcity=\\\"zhongshan\\\" origincode=\\\"QQ0001\\\" />

  </Body></Response>\""
}

还可以写成：

db.dbtestregex.find({data:{ $regex:'<Head>OK<\/Head>'}})

其实现功能一样。

3.类关系型数据库中的 not like 功能实现

反向查询虽然不常见，但也是我们DBA必须的。下面我们做一个案例演示，看看在MongoDB中，怎么实现not like 功能的查询。

需求查询data 字段中不含 <Head>OK</Head>的文档

执行脚本如下：

 db.dbtestregex.find({data:{ $not: /<Head>OK<\/Head>/ }})

返回的文档如下;

{
  "_id" : ObjectId("5d305b1c4857fc49c0c14c81"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b3b4857fc49c0c14c82"),
  "order" : "QQ00001",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b404857fc49c0c14c83"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b454857fc49c0c14c84"),
  "order" : "QQ00002",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b4b4857fc49c0c14c85"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
},
{
  "_id" : ObjectId("5d305b4f4857fc49c0c14c86"),
  "order" : "QQ00003",
  "data" : "\"<?xml version='1.0' encoding='UTF-8'?><Response service=\\\"OrderService\\\">

  <Head>ERR</Head><ERROR>重复下单</ERROR></Response>\""
}

总结

关于MongoDB模糊查询的操作就分享到这里了，希望以上内容可以对大家有一定的帮助，可以学到更多知识。想要看更多MongoDB模糊查询的内容，可以关注其他相关文章。

怎么新建MySQL数据库

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