Shulou(Shulou.com)06/01 Report--

Basic operation addition, deletion, modification and search

Add: insert

Introduction: mongodb stores documents. A document is an object in json format.

Syntax: db.collectionName.isnert (document)

1: add a single document

Db.collectionName.insert ({title:'nice day'})

2: add a single document and specify _ id

Db.collectionName.insert ({_ id:8,age:78,name:'lisi'})

3. Add multiple documents

Db.collectionName.insert (

[

{time:'friday',study:'mongodb'}

{_ id:9,gender:'male',name:'QQ'}

]

)

Delete: remove

Syntax: db.collection.remove (query expressions, options)

Option refers to {justOne:true/false}, whether to delete only one line. Default is false.

Be careful

1: the query expression is still a json object

2: rows matched by query expressions will be deleted.

3: if you do not write query expressions, all documents in collections will be deleted.

Example 1: db.stu.remove ({sn:'001'})

Delete a document with a sn attribute value of '001' in the stu table

Example 2: db.stu.remove ({gender:'m',true})

Delete the document whose gender attribute is m in the stu table, deleting only 1 row.

Change update operation

Change who?-query expression

Change it to what?-- A new value or assignment expression

Operation options-optional parameters

Syntax: db.collection.update (query expressions, new values, options)

Example:

Db.news.update ({name:'QQ'}, {name:'MSN'})

It means to select the document in the news table whose name value is QQ and change its document value to {name:'MSN'}

Result: other columns in the document are also missing, with only _ id and name columns left.

That is, the new document directly replaces the old document instead of modifying it.

If you want to modify a column of the document, you can use the $set keyword

Db.collectionName.update (query, {$set: {name:'QQ'}})

Example:

If you don't want the country field, delete it using the $unset operator:

Assignment expression when modified

$set modifies the value of a column

$unset deletes a column

$rename renames a column

$inc increases a column

SetOnInsert fields that can be added when upsert is true and an insert operation occurs.

Example:

The role of Option:

{upsert:true/false,multi:true/false}

Upsert--- means that if there is no match, the row is inserted directly. (same as replace in mysql)

Example: db.stu.update ({name:'wuyong'}, {$set: {name:'junshiwuyong'}}, {upsert:true})

If there is a name='wuyong' document, it will be modified

If not, this new document will be added

Example:

Db.news.update ({_ id:99}, {upsert:true 123)

No _ id=99 document has been modified, so insert it directly

Multi: means to modify multiple lines (even if the query expression hits multiple lines, only one line will be changed by default. If you want to change multiple lines, you can use this option)

Example:

Db.news.update ({age:21}, {$set: {age:22}}, {multi:true})

Then modify all the age=21 documents in news.

Example:

Check: find, findOne

Syntax: db.collection.find (query expression, query column)

Db.collections.find (expression, {column 1:1, column 2:1})

Example 1:db.stu.find ()

Query all documents, all contents

Example 2: db.stu.find ({}, {gendre:1})

Query the gender property of all documents (the _ id attribute is always checked out by default)

Example:

Example 3: db.stu.find ({}, {gender:1, _ id:0})

Query the gender property of all documents, but not the _ id attribute

Example:

Example 3: db.stu.find ({gender:'male'}, {name:1,_id:0})

Query the name attribute in all documents whose gender attribute value is male

Example:

Operators available when Update

Example:

-> db.user.insert ({name:'lisi',age:12,sex:'male',height:123,area:'haidian'})

-> db.user.update ({name:'lisi'}, {$set: {area:'chaoyang'}, $unset: {height:1}, $inc: {age:1}, $rename: {sex:'gender'}})

Db.user.find ()

{"_ id": ObjectId ("51fc01c4f5de93e1f2856e33"), "age": 13, "area": "chaoyang", "gender": "male", "name": "lisi"}

$setOnInsert-> is equivalent to the default value of the column in mysql

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