Welcome to the first lesson of "A Closer Look at Update Operations in MongoDB". This course builds upon your understanding of basic CRUD operations and data modeling. You've already covered read operations in depth. In this lesson, we will refresh your knowledge of updateOne, updateMany, and the $set operator. Additionally, we'll introduce you to other update operators, which will be discussed in detail in upcoming lessons.

As you may recall from earlier in this course path, there are two main methods for updating documents in a MongoDB database: updateOne for updating a single document and updateMany for updating multiple documents at once. Here's the syntax for both methods:

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1db.collection.updateOne(filter, update, options)
2db.collection.updateMany(filter, update, options)

The filter parameter specifies which documents will be updated, while the update parameter defines how the documents will be updated. The options parameter is optional and can be used to specify additional settings for the update operation.

Below is a single code snippet demonstrating how to use updateOne and updateMany:

mongodb
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1use comic_book_store_db
2
3// updateOne example
4db.comic_books.updateOne(
5  { title: "Iron Man" },
6  { $set: { stock_quantity: 20 } }
7);
8
9// updateMany example
10db.comic_books.updateMany(
11  { published_year: { $lt: 1980 } },
12  { $set: { is_featured: true, stock_quantity: 50 } }
13);

In the updateOne example, we update the stock_quantity for the comic book titled "Iron Man". In the updateMany example, we update all comic books published before 1980, setting their is_featured status to true and their stock_quantity to 50.

To update a document, you can use various operators, not just $set. Here is a list of update operators in MongoDB with a brief explanation of each:

• $set: Sets the value of a field in a document.
• $unset: Removes a field from a document.
• $inc: Increments the value of a field by a specified amount.
• $mul: Multiplies the value of a field by a specified amount.
• $rename: Renames a field.
• $min: Updates the field only if the specified value is less than the existing field value.
• $max: Updates the field only if the specified value is greater than the existing field value.
• $currentDate: Sets the value of a field to the current date.

In this lesson, we will focus on refreshing our knowledge of the $set operator. Other operators will be covered in subsequent lessons.

For more detailed information about each operator, refer to the official documentation: MongoDB Update Operators.

To update nested fields within embedded documents, you can use dot notation, similar to how it’s used in read queries. Remember to enclose the field names in quotes when using dot notation to avoid errors.

mongodb
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1use comic_book_store_db
2
3db.comic_books.updateOne(
4  { title: "Iron Man" },
5  { $set: { "writer.name": "Stan Lee" } }
6);

In this example, we update the name field within the writer embedded document for the comic book titled "Iron Man".

In this lesson, we revisited the updateOne and updateMany functions, along with the $set operator. We also introduced other update operators such as $unset, $inc, $mul, $rename, $min, $max, and $currentDate, which will be explored in more detail in future lessons. Make sure to review these concepts as they will form the foundation for the upcoming practices and lessons in this course. Happy coding!