Explanation:If applications do not specify a value for _id the driver or the mongod will create an _id field with an ObjectId value. 4. The ______ index is unique and prevents clients from inserting two documents with the same value for the _id field.
A. _id
B. $default
C. _def
D. None of the mentioned
Answer:A
Explanation:If applications do not specify a value for _id the driver or the mongod will create an _id field with an ObjectId value. 4. The ______ index is unique and prevents clients from inserting two documents with the same value for the _id field.
A. _id B. $default C. _def D. None of the mentioned
Explanation:All MongoDB collections have an index on the _id field that exists by default. 5. Point out the wrong statement :