Which SQL statement below does the following MongoDB script most closely correspond to?

db.students.find( {age: 18}, {name: 1, _id :0} )

Question

Which SQL statement below does the following MongoDB script most closely correspond to?

db.students.find( {age: 18}, {name: 1, _id :0} )

BlackTom AI · Accepted Answer

The SQL equivalent is: SELECT name FROM students WHERE age=18.

Relevant knowledge points:
- MongoDB db.collection.find(filter, projection) takes two arguments: the filter (query) selects documents, and the projection controls which fields are returned (1 to include, 0 to exclude).
- In the filter {age: 18}, documents must have age equal to 18 — this corresponds to SQL’s WHERE age = 18.
- The projection {name: 1, _id: 0} means include the name field and exclude the MongoDB default _id field. SQL requires explicitly listing the columns to return, so you would SELECT name.

Step-by-step mapping:
1. Filter mapping: {age: 18} → WHERE age = 18.
2. Projection mapping: {name: 1} → SELECT name. The additional {_id: 0} only removes the MongoDB _id field; in SQL you simply do not include _id in the SELECT list.
3. Combine: SELECT name FROM students WHERE age = 18.

Why the correct answer is correct:
- The MongoDB script returns only the name field for documents where age equals 18. The SQL statement SELECT name FROM students WHERE age=18 returns exactly that set of values from the students table.

Why the other options are incorrect:
- Option 1 (SELECT age FROM students WHERE name IS NOT NULL) uses the wrong selected column and a different condition (name IS NOT NULL vs age = 18).
- Option 2 (SELECT * FROM students WHERE age=18 AND name IS NOT NULL) selects all columns and adds an extra constraint (name IS NOT NULL) not present in the Mongo query; projection does not impose a non-null requirement.
- Option 3 (SELECT * FROM students WHERE age=18 AND name=1 AND _id=0) misinterprets projection keys (1/0) as equality tests; projection does not translate into WHERE name=1 or _id=0 and selecting * returns all columns.

Final confirmation: The correct SQL statement is SELECT name FROM students WHERE age=18, which matches the provided answer.

Which SQL statement below does the following MongoDB script most closely correspond to? db.students.find( {age: 18}, {name: 1, _id :0} ) 单项选择题

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