ensure

英[?n'???(r)] US[?n???r]

vt. Ensure; guarantee to obtain [avoid]; make (someone) Get; make safe

index

## English[??ndeks] US[??n?d?ks]

n.index;<number>index;instruction; Sign

vt.Index...;Index...;[Economics]Adjust by living index (wage, price, etc.)

vi.[Mechanics]Transposition

MongoDB ensureIndex() method syntax

Function: MongoDB uses the ensureIndex() method to create indexes.

Syntax: >db.COLLECTION_NAME.ensureIndex({KEY:1}) In the syntax, the Key value is the index field you want to create, and 1 specifies to create the index in ascending order. If you If you want to create indexes in descending order, specify -1.

MongoDB ensureIndex() method example

>db.col.ensureIndex({"title":1})
>
ensureIndex() 方法中你也可以設(shè)置使用多個(gè)字段創(chuàng)建索引（關(guān)系型數(shù)據(jù)庫(kù)中稱(chēng)作復(fù)合索引）。

>db.col.ensureIndex({"title":1,"description":-1})
>