MongoDB $mul Operator: Field Update and Creation
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Questions and Answers

What is the purpose of the updateOne() method in MongoDB?

  • Updates a single document that satisfies a filter (correct)
  • Updates multiple documents that satisfy a filter
  • Deletes a document from the collection
  • Inserts a new document into the collection

    • Which operator is used to increment a field by a specified value in MongoDB update operations?

  • $inc (correct)
  • $push
  • $set
  • $add

    • What happens if the $inc operator is used on a field with a null value in MongoDB?

  • It increments the null value by the specified amount
  • It deletes the field
  • It generates an error (correct)
  • It creates the field and sets it to the specified value

    • When using the updateMany() method in MongoDB, what does it do?

    <p>Updates all documents in the collection</p> Signup and view all the answers

    In MongoDB, what is the purpose of the $set operator in update operations?

    <p>Updates existing fields with new values</p> Signup and view all the answers

    How would you update the 'salary' field from 70000 to 85000 for documents in the 'employees' collection in MongoDB?

    <p>{ $set: { salary: 85000 } }</p> Signup and view all the answers

    What does the $inc operator do in the 'db.updateopr.updateOne({_id:1}, {$inc:{qty:2}})' query?

    <p>Increase the qty field by 2</p> Signup and view all the answers

    Which query decreases the quantity field by 2?

    <p>db.updateopr.updateOne({_id:1}, {$inc:{qty:-2}})</p> Signup and view all the answers

    What is the purpose of the $rename operator in MongoDB update operations?

    <p>Updates the name of a field</p> Signup and view all the answers

    How does the $rename operator handle conflicts when updating the name of a field?

    <p>Performs an $unset of both old and new names and then a $set operation with the new name</p> Signup and view all the answers

    Which type of fields can the $rename operator rename using dot operator in MongoDB?

    <p>Fields in embedded documents</p> Signup and view all the answers

    In MongoDB, what happens when the document already has a field with the new name while using the $rename operator?

    <p>$rename removes that field and renames the specified one</p> Signup and view all the answers

    What does the $set operator do in MongoDB?

    <p>Replaces the value of a field with the specified value</p> Signup and view all the answers

    In MongoDB, how does $set behave when specifying multiple field-value pairs?

    <p>Updates or creates each field</p> Signup and view all the answers

    When using $set in MongoDB, what happens if the field being updated does not exist?

    <p>A new field is added with the specified value</p> Signup and view all the answers

    How can you update a top-level field in MongoDB using the $set operator?

    <p>Use dot notation</p> Signup and view all the answers

    What do you need to use to specify a field within an embedded document in MongoDB?

    <p>Dot notation</p> Signup and view all the answers

    In MongoDB, how does $set behave when updating array elements?

    <p>It appends new elements without replacing existing ones</p> Signup and view all the answers

    What does the $min operator do in MongoDB?

    <p>Updates the field to a specified value if the specified value is less than the current value</p> Signup and view all the answers

    In MongoDB, what happens if the field does not exist when using the $min operator?

    <p>The field is set to the specified value</p> Signup and view all the answers

    How does the $min operator treat existing fields when updating?

    <p>Updates only if the current value is less than the new value</p> Signup and view all the answers

    When using $max in MongoDB, what does it do if the specified value is greater than the current value of the field?

    <p>Updates the field to the new value</p> Signup and view all the answers

    What does the $max operator do when updating a field that does not exist?

    <p>Sets the field to a specified value</p> Signup and view all the answers

    In MongoDB, what is the functionality of $max operator when comparing numbers?

    <p>Updates to a specified value if greater than current value</p> Signup and view all the answers

    What happens when applying the $mul operator to a field that is not in the document?

    <p>The field is created and the value is set to zero</p> Signup and view all the answers

    What is the syntax for applying the $mul operator to a field in an embedded document or array?

    <p>{ field: { $mul: value } }</p> Signup and view all the answers

    If the price field has a value of 10.99 and the quantity field has a value of 25, what will be the result after applying $mul to these fields?

    <p>Price becomes 13.74, quantity becomes 50</p> Signup and view all the answers

    What will be the type of the value in the 'price' field after using the $mul operator to multiply Decimal128(10) by Int32(5)?

    <p>Decimal128</p> Signup and view all the answers

    What may happen when multiplying values of mixed numeric types using the $mul operator?

    <p>Conversion of numeric types may occur</p> Signup and view all the answers

    What is the outcome if a document already contains a price field and the $mul operator is applied to it?

    <p>The existing price field will be updated with the new value</p> Signup and view all the answers

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