Question

The command db.students.find({same:"Lisa"}) will find all student documents with sname = "Lisa". How do you find the first document in the list of the found documents?

A) db.students.findOne({same:"Lisa"})
B) db.students.find({same:"Lisa"}).limit(1)
C) db.students.find({same:"Lisa"}).sort(_id:1).limit(1)
D) all fo the above
E) none of the above

Answer 1

To find the first document where the field sname is equal to "Lisa" in a MongoDB collection, you can use db.students.findOne({sname:"Lisa"}), which is the most straightforward method, but options B and C would also work, making the answer D, all of the above.

Step-by-step explanation:

The command you mentioned appears to be related to using MongoDB, which is a NoSQL database program. Retrieving a single document from the collection of student documents where the field sname is equal to "Lisa" can be done in several ways. Option A, using db.students.findOne({sname:"Lisa"}), will indeed find the first document that matches the query. Option B, using db.students.find({sname:"Lisa"}).limit(1), will return a cursor to the first document as well. Option C, db.students.find({sname:"Lisa"}).sort({_id:1}).limit(1), is a bit redundant because findOne inherently returns the first match it finds (which is usually sorted by the internal _id field by default), but it would also work. Therefore, the correct answer is D, as all of the options provided would achieve the desired result of finding the first document with sname equal to "Lisa".