MongoDB Common Command Summary _mongodb

Simple additions and deletions to check the data

Specify the display in the query results or do not display a field

For example, we want to find all the data in the lessons collection, but we don't want to include the Slides field in the return result, because slides is a huge array of base64-represented images that affect the reading of query results.
Then we can follow the query object with an argument. As follows:

Copy Code code as follows:

Db.lessons.find ({}, {slides:0});

You can also explicitly specify which fields to display:

Copy Code code as follows:

Db.bios.find (
{ },
{name:1, contribs:1, _id:0}
)

Comparison operations – greater than and less than

We want to query the time range between StartTime and Endtime data records, while requiring content to be the number 1 to 5.

Copy Code code as follows:

Db.wemessages.find ({$and: [
{createtime: {$gt: (Starttime.gettime ()/1000). ToString ()}},
{createtime: {$lt: (Endtime.gettime ()/1000). ToString ()}},
{Content: {$in: [' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 '}}}
]}
);

Here we use $and logical operators, and $GT, $LT, $in comparison operators.

For MongoDB operators, see: http://docs.mongodb.org/manual/reference/operator/query/

Update some properties of a record

Using the $set means that only the specified fields are updated without modifying other fields, which we would normally be.

Copy Code code as follows:

Db.lessons.update ({}, {$set: {' course_id ': ' C.101 '}});

Update more than one record

Use {multi:true}

Copy Code code as follows:

Db.lessons.update ({}, {$set: {' course_id ': ' C.101 '}}, {multi:true});
Db.muusers.update ({username: ' Tom '}, {$set: {mobile: ' 6508639713 '}}, {multi:true});

Sort Query Results

Using the Sort method

Copy Code code as follows:

Db.muusers.find (). Sort ({firsttime:-1});

-1 Descending, 1 ascending

View query results with refreshing

Using the Pretty method

Copy Code code as follows:

Db.lessons.find ({lesson:1}, {slides:0, mp3voice:0, wavvoice:0, wavvoicemin:0}). Pretty ();

View records that do not exist in a field

Use $exists

Copy Code code as follows:

Db.questions.find ({' sequence_id ': 1, ' pngslide ': {$exists: false}});
Db.mycollection.find ({"Price": {"$exists": false}})

Limit the number of query results limit and skip the number of records that started skip

Using Limit and Skip

Copy Code code as follows:

Db.translation_memory.find ({mp3voice: {$exists: false}}, NULL, {limit:100});

Delete all content in collection

Remove method Using Collection

Copy Code code as follows:

Db.collection.remove ();

Get the length of a field in collection

Chained call

Copy Code code as follows:

Db.lessons.find ({lesson:1}). ToArray () [0].slides.join ('). length

Collection operation

Renamed Collection

Using the Renamecollection method

Copy Code code as follows:

Db.quizzes.renameCollection (' questions ');

Delete a field

Use $unset

Copy Code code as follows:

Db.questions.update ({}, {$unset: {quiz_name:1}}, {multi:true});
Db.learning_progress.update ({}, {$unset: {lesson:1}}, {multi:true});
Db.lessons.update ({}, {$unset: {wavvoice:1, Wavvoicemin:1}}, {multi:true});

Modify the name of a field

Use $rename

Copy Code code as follows:

Db.students.update ({_id:1}, {$rename: {' nickname ': ' Alias ', ' cell ': ' Mobile '}})

Note: Some MongoDB keywords cannot be used as collection names, for example, group.

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