In this guide, I will cover the $unset operator in MongoDB inside the mongo shell.
The $unset operator is used to remove a field from documents. this tutorial will walk you through a quick and easy guide to use the $unset operator inside the mongo shell.
To read the Nodejs driver tutorial with examples on using the $unset operator with the Mongoose ODM, click the post below.
Related Post: Remove a Field Completely from a MongoDB Document
This guide will demonstrate with examples, how to use the unset operator to remove a field in MongoDB.
The $unset Operator Syntax (Mongo Shell)
Let us look at the mongo shell syntax of the $unset operator in MongoDB:
{ $unset: { field1: "", ... } }
Using the $unset Operator inside the Mongo Shell
Let us start with the examples to learn to use the $unset operator in MongoDB inside the Mongo shell.
Using the $unset Operator on Fields in MongoDB
In this example, I will use the $unset operator to remove a field inside our documents.
- Start the mongo local database server
- Open the mongo shell and navigate into a database using the use db_name command
- Let us take a look at our documents available:
> db.shoes.find({}).pretty()
{
"_id" : ObjectId("616b18a556e71503e4a0334d"),
"name" : "Mariana Grider Boots",
"price" : 23000,
"size" : 7,
"style" : "Slingbacks",
"onSale" : false,
"freeDelivery" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 40,
"colors" : " "
}
}
{
"_id" : ObjectId("616b18a556e71503e4a0334e"),
"name" : "Purple Shimmery Heels",
"price" : 13380,
"size" : 6,
"style" : "Peep Toes",
"onSale" : true,
"freeDelivery" : false,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
},
"itemNumber" : 0
}
{
"_id" : ObjectId("616b18a556e71503e4a0334f"),
"name" : "Zac Porter Straps",
"price" : 19760,
"size" : 8,
"style" : "Ankle Strap",
"onSale" : true,
"freeDelivery" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("616b18a556e71503e4a03350"),
"name" : "Valerina's Red Carpet Toes",
"price" : 26000,
"size" : 9,
"style" : "Scarpin",
"onSale" : false,
"freeDelivery" : false,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("616b18a556e71503e4a03351"),
"name" : "Neeta Parmar's Stylish Bees 'n' Honey Boots",
"price" : 10780,
"size" : 7,
"style" : "Wedge Booties",
"onSale" : true,
"freeDelivery" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("6171bbf968378cae00d83aca"),
"name" : "Caroline Wielder Shoes",
"price" : NumberDecimal("14999.985"),
"size" : 5,
"style" : "Wedge Booties",
"onSale" : true,
"freeDelivery" : false,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("6171bbf968378cae00d83acb"),
"name" : "Marilyn Jaworski Sky Highs",
"price" : NumberDecimal("12399.85"),
"size" : 5,
"style" : "Scarpin",
"onSale" : false,
"freeDelivery" : false,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
- Let’s say we want to remove the freeDelivery field from all our documents. We will use the $unset operator to help us out:
> db.shoes.updateMany(
... { },
... { $unset: { "freeDelivery" : "" } }
... )
{ "acknowledged" : true, "matchedCount" : 7, "modifiedCount" : 7 }
- Let us have a look at our documents:
> db.shoes.find({}).pretty()
{
"_id" : ObjectId("616b18a556e71503e4a0334d"),
"name" : "Mariana Grider Boots",
"price" : 23000,
"size" : 7,
"style" : "Slingbacks",
"onSale" : false,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 40,
"colors" : " "
}
}
{
"_id" : ObjectId("616b18a556e71503e4a0334e"),
"name" : "Purple Shimmery Heels",
"price" : 13380,
"size" : 6,
"style" : "Peep Toes",
"onSale" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
},
"itemNumber" : 0
}
{
"_id" : ObjectId("616b18a556e71503e4a0334f"),
"name" : "Zac Porter Straps",
"price" : 19760,
"size" : 8,
"style" : "Ankle Strap",
"onSale" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("616b18a556e71503e4a03350"),
"name" : "Valerina's Red Carpet Toes",
"price" : 26000,
"size" : 9,
"style" : "Scarpin",
"onSale" : false,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("616b18a556e71503e4a03351"),
"name" : "Neeta Parmar's Stylish Bees 'n' Honey Boots",
"price" : 10780,
"size" : 7,
"style" : "Wedge Booties",
"onSale" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("6171bbf968378cae00d83aca"),
"name" : "Caroline Wielder Shoes",
"price" : NumberDecimal("14999.985"),
"size" : 5,
"style" : "Wedge Booties",
"onSale" : true,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
{
"_id" : ObjectId("6171bbf968378cae00d83acb"),
"name" : "Marilyn Jaworski Sky Highs",
"price" : NumberDecimal("12399.85"),
"size" : 5,
"style" : "Scarpin",
"onSale" : false,
"moreDetails" : {
"qtyAvlbl" : 10,
"colors" : " "
}
}
We have successfully deleted or removed the freeDelivery field from all our documents using the $unset operator in MongoDB.
Using the $unset Operator on Nested Documents in MongoDB
We will now remove an embedded field or document from our documents using the $unset operator.
> db.shoes.updateMany(
... { },
... { $unset: { "moreDetails.colors" : "" } }
... )
{ "acknowledged" : true, "matchedCount" : 7, "modifiedCount" : 7 }
- Let us take a look at our documents now:
> db.shoes.find({}).pretty()
{
"_id" : ObjectId("616b18a556e71503e4a0334d"),
"name" : "Mariana Grider Boots",
"price" : 23000,
"size" : 7,
"style" : "Slingbacks",
"onSale" : false,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 40
}
}
{
"_id" : ObjectId("616b18a556e71503e4a0334e"),
"name" : "Purple Shimmery Heels",
"price" : 13380,
"size" : 6,
"style" : "Peep Toes",
"onSale" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10
},
"itemNumber" : 0
}
{
"_id" : ObjectId("616b18a556e71503e4a0334f"),
"name" : "Zac Porter Straps",
"price" : 19760,
"size" : 8,
"style" : "Ankle Strap",
"onSale" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10
}
}
{
"_id" : ObjectId("616b18a556e71503e4a03350"),
"name" : "Valerina's Red Carpet Toes",
"price" : 26000,
"size" : 9,
"style" : "Scarpin",
"onSale" : false,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10
}
}
{
"_id" : ObjectId("616b18a556e71503e4a03351"),
"name" : "Neeta Parmar's Stylish Bees 'n' Honey Boots",
"price" : 10780,
"size" : 7,
"style" : "Wedge Booties",
"onSale" : true,
"__v" : 0,
"moreDetails" : {
"qtyAvlbl" : 10
}
}
{
"_id" : ObjectId("6171bbf968378cae00d83aca"),
"name" : "Caroline Wielder Shoes",
"price" : NumberDecimal("14999.985"),
"size" : 5,
"style" : "Wedge Booties",
"onSale" : true,
"moreDetails" : {
"qtyAvlbl" : 10
}
}
{
"_id" : ObjectId("6171bbf968378cae00d83acb"),
"name" : "Marilyn Jaworski Sky Highs",
"price" : NumberDecimal("12399.85"),
"size" : 5,
"style" : "Scarpin",
"onSale" : false,
"moreDetails" : {
"qtyAvlbl" : 10
}
}
We have successfully removed the colors nested document from all our documents.
Using the $unset Operator on Missing or Non-Existent Fields
Let us try removing a field that does not exist in any of our documents:
> db.shoes.updateMany(
... { },
... { $unset: { "isAvailable" : "" } }
... )
{ "acknowledged" : true, "matchedCount" : 7, "modifiedCount" : 0 }
The modifiedCount property shows a 0 value which indicates the operation was no-op meaning, it did not change anything.
Conclusion
In this article, we learned how to use the $unset Operator in MongoDB with multiple examples. If you are interested in more such tutorials, keep a tab on the latest releases at CodeForGeek.com
