MongoDB command exercise (Advanced)

For more information about data comparison and other instructions can be found in official documents

$eq	=
$gt	>
$gte	>=
$lt	<
$ lte	<=
$ does	!=

// 18. Num query document numbers in the 500

db.numbers.find({num:500})

19 // Query numbers in num is greater than 5000 documents

db.numbers.find({num:{$gt:500}});
db.numbers.find({num:{$eq:500}});

// 20. Num query numbers in less than 30 documents

db.numbers.find({num:{$lt:30}});

21 // Query numbers in num is greater than 40 documents less than 50

db.numbers.find({num:{$gt:40 , $lt:50}});

22 // Query numbers in num is greater than the document 19996

db.numbers.find({num:{$gt:19996}});

// 23 View the first 10 numbers in the collection of data

db.numbers.find({num:{$lte:10}});//具有特殊性，数据是有序的

// limit () Set the upper limit of the display data

db.numbers.find().limit(10);

// in the development, we will not execute the query without conditions

db.numbers.find();

// 24. See the article in a set of numbers 11 through 20 of data
/ *
page 10 per
1-10 0
11-20 10
21-30 20 is
. . .

    skip((页码-1) * 每页显示的条数).limit(每页显示的条数);
    
skip()用于跳过指定数量的数据    

MongoDB会自动调整skip和limit的位置
db.numbers.find().skip(10).limit(10);

// 25 View Article 21-30 numbers in the collection of data

db.numbers.find().skip(20).limit(10);

db.numbers.find().limit(10).skip(10);