Returning Specific Data from a Query in MongoDB

Review the following code, which demonstrates how to return selected fields from a query.

Add a Projection Document

To specify fields to include or exclude in the result set, add a projection document as the second parameter in the call to db.collection.find().

Syntax:

db.collection.find( <query>, <projection> )

Include a Field

To include a field, set its value to 1 in the projection document.

Syntax:

db.collection.find( <query>, { <field> : 1 })

Example:

// Return all restaurant inspections - business name, result, and _id fields only
db.inspections.find(
  { sector: "Restaurant - 818" },
  { business_name: 1, result: 1 }
)

Exclude a Field

To exclude a field, set its value to 0 in the projection document.

Syntax:

db.collection.find(query, { <field> : 0, <field>: 0 })

Example:

// Return all inspections with result of "Pass" or "Warning" - exclude date and zip code
db.inspections.find(
  { result: { $in: ["Pass", "Warning"] } },
  { date: 0, "address.zip": 0 }
)

While the _id field is included by default, it can be suppressed by setting its value to 0 in any projection.

// Return all restaurant inspections - business name and result fields only
db.inspections.find(
  { sector: "Restaurant - 818" },
  { business_name: 1, result: 1, _id: 0 }
)