Use regular selectors ($regex) in MongoDB query documents

We have introduced the use of text selectors ($text) to query documents before, if you need to know more, you can refer to:

Use text selector ($text) in MongoDB query document https://blog.csdn.net/m1729339749/article/details/130605491

In this article, we introduce the use of the $regex selector to query documents:

1. Preparation

Initialize student information data

db.studentInfos.insertMany([
    { "_id": 1, "name": "张三1", "sports": "羽毛球、乒乓球", fruits: "apple, banana", introduce: "大家好，我喜欢运动，但是我不喜欢铅球，因为它太重了" },
    { "_id": 2, "name": "李四1", "sports": "篮球、乒乓球、跑步", fruits: "Apple", introduce: "大家好，我喜欢水果，但是不喜欢吃橘子，因为它太酸了" },
    { "_id": 3, "name": "王五1", "sports": "足球、羽毛球", fruits: "Banana", introduce: "大家好，我喜欢水果，喜欢运动" },
    { "_id": 4, "name": "张三2", "sports": "网球、铅球", fruits: "orange", introduce: "大家好，我喜欢水果与健身" },
    { "_id": 5, "name": "李四2", "sports": "乒乓球", fruits: "Orange, Apple", introduce: "大家好，我喜欢乒乓球运动" },
    { "_id": 6, "name": "王五2", "sports": "篮球", fruits: "Orange, Banana", introduce: "hello，i like sports" },
    { "_id": 7, "name": "张三3", "sports": "跑步、跳绳", fruits: "Orange, apple, Banana", introduce: "haha, 与健身相比，我更喜欢吃" },
    { "_id": 8, "name": "李四3", "sports": "足球", fruits: "orange, banana", introduce: "足球和橘子是我的最爱" },
    { "_id": 9, "name": "王五3", "sports": "跆拳道", fruits: "Banana", introduce: "我不喜欢健身，我喜欢突破自己" }
])

2. Regular selector ($regex)

grammar:

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

The above three syntaxes are all used for regular expression retrieval.

/pattern/: represents the pattern regular expression object

'pattern': the pattern representing the regular expression text

$options: represents options,

        i: case insensitive

        m: Anchor points are included in the regular expression (^ represents the beginning, $ represents the end)

3. Example: Retrieve documents containing apple in furits

The command to query the document is as follows:

db.studentInfos.find({
    fruits: { $regex: /apple/, $options: '' }
})

 Equivalent to:

db.studentInfos.find({
    fruits: { $regex: /apple/ }
})

Equivalent to:

db.studentInfos.find({
    fruits: /apple/
})

The results of the query document are as follows:

{ "_id" : 1, "name" : "张三1", "sports" : "羽毛球、乒乓球", "fruits" : "apple, banana", "introduce" : "大家好，我喜欢运动，但是我不喜欢铅球，因为它太重了" }
{ "_id" : 7, "name" : "张三3", "sports" : "跑步、跳绳", "fruits" : "Orange, apple, Banana", "introduce" : "haha, 与健身相比，我更喜欢吃" }

4. Example: Retrieve documents containing apple in furits (case insensitive)

In the above example, we found that the documents with Apple in fruits were not retrieved, because the retrieved text is case-sensitive by default. If it is not case-sensitive, you can use the following query command:

db.studentInfos.find({
    fruits: { $regex: /apple/, $options: 'i' }
})

Equivalent to:

db.studentInfos.find({
    fruits: { $regex: /apple/i }
})

Equivalent to:

db.studentInfos.find({
    fruits: /apple/i
})

The results of the query document are as follows:

{ "_id" : 1, "name" : "张三1", "sports" : "羽毛球、乒乓球", "fruits" : "apple, banana", "introduce" : "大家好，我喜欢运动，但是我不喜欢铅球，因为它太重了" }
{ "_id" : 2, "name" : "李四1", "sports" : "篮球、乒乓球、跑步", "fruits" : "Apple", "introduce" : "大家好，我喜欢水果，但是不喜欢吃橘子，因为它太酸了" }
{ "_id" : 5, "name" : "李四2", "sports" : "乒乓球", "fruits" : "Orange, Apple", "introduce" : "大家好，我喜欢乒乓球运动" }
{ "_id" : 7, "name" : "张三3", "sports" : "跑步、跳绳", "fruits" : "Orange, apple, Banana", "introduce" : "haha, 与健身相比，我更喜欢吃" }

5. Example: Retrieve the first document of apple in furits (case insensitive)

The command to query the document is as follows:

db.studentInfos.find({
    fruits: { $regex: /^apple/, $options: 'im' }
})

Equivalent to:

db.studentInfos.find({
    fruits: { $regex: /^apple/im }
})

Equivalent to:

db.studentInfos.find({
    fruits: /^apple/im
})

The results of the query document are as follows:

{ "_id" : 1, "name" : "张三1", "sports" : "羽毛球、乒乓球", "fruits" : "apple, banana", "introduce" : "大家好，我喜欢运动，但是我不喜欢铅球，因为它太重了" }
{ "_id" : 2, "name" : "李四1", "sports" : "篮球、乒乓球、跑步", "fruits" : "Apple", "introduce" : "大家好，我喜欢水果，但是不喜欢吃橘子，因为它太酸了" }

6. Example: Retrieve the document that the last one in furits is apple (case insensitive)

The command to query the document is as follows:

db.studentInfos.find({
    fruits: { $regex: /apple$/, $options: 'im' }
})

Equivalent to:

db.studentInfos.find({
    fruits: { $regex: /apple$/im }
})

Equivalent to:

db.studentInfos.find({
    fruits: /apple$/im
})

The results of the query document are as follows:

{ "_id" : 2, "name" : "李四1", "sports" : "篮球、乒乓球、跑步", "fruits" : "Apple", "introduce" : "大家好，我喜欢水果，但是不喜欢吃橘子，因为它太酸了" }
{ "_id" : 5, "name" : "李四2", "sports" : "乒乓球", "fruits" : "Orange, Apple", "introduce" : "大家好，我喜欢乒乓球运动" }