// $eq
db.projects.find({cost: {$eq: 2000}});

// $ne
db.projects.find({cost: {$ne: 2000}}).pretty();

// $exists
db.projects.find({cost: {$exists: true}}).pretty();

// $gt - $lt
db.projects.find({cost: {$gt: 10000}}).pretty();
db.projects.find({cost: {$gte: 10000}}).pretty();
db.projects.find({cost: {$lt: 10000}}).pretty();
db.projects.find({cost: {$lte: 10000}}).pretty();

// $in
db.projects.find({
	category: {$in:['Web Deisgn', 'Web Programming']}
}).pretty();

// $and - $or
db.projects.find({$or: [{cost: {$eq: 2000}}, {cost: {$gt: 10000}}]});

db.projects.find({$and: [{category: {$eq: 'Mobile Programming'}}, {cost: {$gt: 10000}}]});

db.projects.aggregate({$limit: 2});
db.projects.aggregate({$skip: 2});
db.projects.aggregate({$sort: {name: 1}}).pretty();
db.projects.aggregate([{$match: {name: 'Company Website'}}]);

db.projects.aggregate([
	{$project: {projectDescription:{$concat:["$name"," - ", "$category"]}}}
]);