MongoDB 正则表达式
在 MongoDB 中，正则表达式用于模式匹配，基本上是在文档中的字符串中搜索模式。它是一种将模式与字符序列匹配的通用方法。$regex 运算符用作正则表达式来查找字符串中的模式。
在 MongoDB 中，我们可以通过两种不同的方式进行模式匹配：
- 使用 $regex 运算符进行模式匹配
- 没有 $regex 运算符的模式匹配
使用 $regex 运算符进行模式匹配
在 MongoDB 中，$regex 运算符提供了查询中模式匹配的功能。换句话说，$regex 运算符用于搜索文档中的特定字符串。
语法：
{ <field>: { $regex: /pattern/, $options: '<options>' } }
{ <field>: { $regex: 'pattern', $options: '<options>' } }
$options:
以下 <option> 可与正则表达式一起使用：
- “i”字符用于匹配字符串中的小写和大写模式。
- “^”和“$”符号用于搜索文档中的特定模式。“^”符号用于确保字符串以某个字符开头，$ 用于确保字符串以某个字符结尾。
- “x”字符用于忽略字符串中的所有空白字符。
例子：
在以下示例中，我们正在使用：
Database: Yiidian
Collection: student
Document: Five documents that contain the details of the students
>db.student.find()
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d65f"),
"name" : "Mick",
"Course" : "btech",
"batch_year" : 2018,
"language" : ["c++", "java", "python"],
"personal_details" :
{
"Father_name" : "Jonny",
"phone_no" : 8895321456,
"age" : 23,
"gender" : "Male",
"City" : "NewYork",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d691"),
"name" : "MIck99",
"Course" : "BCA",
"batch_year" : 2020,
"language" : ["C#", "JavaScript"],
"personal_details" :
{
"Father_name" : "Henry",
"phone_no" : 9874563698,
"age" : 20,
"gender" : "Female",
"City" : "London",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d655"),
"name" : "Jonny",
"Course" : "MCALE",
"batch_year" : 2019,
"language" : ["C#", "java", "PHP"],
"personal_details" :
{
"Father_name" : "Thomas",
"phone_no" : 7845123698,
"age" : 24,
"gender" : "Male",
"City" : "London",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d678"),
"name" : "Oliver",
"Course" : "MCA",
"batch_year" : 2017,
"language" : ["c", "PHP"],
"personal_details" :
{
"Father_name" : "William",
"phone_no" : 9997845123,
"age" : 25,
"gender" : "Male",
"City" : "Liverpool",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d665"),
"name" : "mia",
"Course" : "btech",
"batch_year" : 2020,
"language" : ["HTML", "CSS", "PHP"],
"personal_details" :
{
"Father_name" : "Leo",
"phone_no" : 6312547896,
"age" : 22,
"gender" : "Female",
"City" : "Manchester",
}
}
示例 1：显示正在攻读 B.Tech 的学生的详细信息。
我们正在显示课程为 btech 的学生的详细信息，因此我们使用 $regex 运算符（即 {$regex : "btech"}）为 find() 方法中的课程字段传递一个正则表达式。
>db.student.find({Course : {$regex: "btech" }}).forEach(printjson)
输出结果为：
>db.student.find({Course : {$regex: "btech" }}).forEach(printjson)
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d65f"),
"name" : "Mick",
"Course" : "btech",
"batch_year" : 2018,
"language" : ["c++", "java", "python"],
"personal_details" :
{
"Father_name" : "Jonny",
"phone_no" : 8895321456,
"age" : 23,
"gender" : "Male",
"City" : "NewYork",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d665"),
"name" : "mia",
"Course" : "btech",
"batch_year" : 2020,
"language" : ["HTML", "CSS", "PHP"],
"personal_details" :
{
"Father_name" : "Leo",
"phone_no" : 6312547896,
"age" : 22,
"gender" : "Female",
"City" : "Manchester",
}
}
示例 2：使用 i <options> 显示姓名以“Mi”开头的学生的详细信息。
>db.student.find({ name :{$regex: "Mi" ,$options: 'i' }}).forEach(printjson)
输出结果为：
>db.student.find({name:{$regex: "Mi",$options:'i'}}).forEach(printjson)
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d65f"),
"name" : "Mick",
"Course" : "btech",
"batch_year" : 2018,
"language" : ["c++", "java", "python"],
"personal_details" :
{
"Father_name" : "Jonny",
"phone_no" : 8895321456,
"age" : 23,
"gender" : "Male",
"City" : "NewYork",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d691"),
"name" : "MIck99",
"Course" : "BCA",
"batch_year" : 2020,
"language" : ["C#", "JavaScript"],
"personal_details" :
{
"Father_name" : "Henry",
"phone_no" : 9874563698,
"age" : 20,
"gender" : "Female",
"City" : "London",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d665"),
"name" : "mia",
"Course" : "btech",
"batch_year" : 2020,
"language" : ["HTML", "CSS", "PHP"],
"personal_details" :
{
"Father_name" : "Leo",
"phone_no" : 6312547896,
"age" : 22,
"gender" : "Female",
"City" : "Manchester",
}
}
示例 3：显示课程为 MCA 的学生的详细信息。
>db.student.find({Course : {$regex: "^MCA$"}}).forEach(printjson)
输出结果为：
>db.student.find({Course : {$regex: "^MCA$"}}).forEach(printjson)
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d678"),
"name" : "Oliver",
"Course" : "MCA",
"batch_year" : 2017,
"language" : ["c", "PHP"],
"personal_details" :
{
"Father_name" : "William",
"phone_no" : 9997845123,
"age" : 25,
"gender" : "Male",
"City" : "Liverpool",
}
}
没有 $regex 运算符的模式匹配
在 MongoDB 中，我们可以在不使用 $regex 运算符的情况下进行模式匹配。在此方法中，它使用正则表达式对象。
语法：
{ <field>: /pattern/<options> }
示例 4：使用正则表达式对象显示姓名中包含“ck”的学生的详细信息。
>db.student.find({ name : /ck/}).forEach(printjson)
“//”表示在这些分隔符中指定您的搜索条件。因此，我们正在寻找名称中包含“CK”的文档。
输出结果为：
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d65f"),
"name" : "Mick",
"Course" : "btech",
"batch_year" : 2018,
"language" : ["c++", "java", "python"],
"personal_details" :
{
"Father_name" : "Jonny",
"phone_no" : 8895321456,
"age" : 23,
"gender" : "Male",
"City" : "NewYork",
}
}
{
"_id" : ObjectId("56254d4fdf2222265r4g12ds3d691"),
"name" : "MIck99",
"Course" : "BCA",
"batch_year" : 2020,
"language" : ["C#", "JavaScript"],
"personal_details" :
{
"Father_name" : "Henry",
"phone_no" : 9874563698,
"age" : 20,
"gender" : "Female",
"City" : "London",
}
}
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