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Queries

Queries to the database are made in JSON format. The following operators are supported:

  • $eq: Matches documents where the value of a field equals the specified value.
  • $gt: Matches documents where the value of a field is greater than the specified value.
  • $gte: Matches documents where the value of a field is greater than or equal to the specified value.
  • $lt: Matches documents where the value of a field is less than the specified value.
  • $lte: Matches documents where the value of a field is less than or equal to the specified value.
  • $ne: Matches documents where the value of a field does not equal the specified value.
  • $in: Matches any of the values specified in an array.
  • $nin: Matches none of the values specified in an array.
  • $exists: Matches documents where the specified field exists.
  • $regex: Matches documents where the value of a field matches a regular expression.
  • $and: Joins query clauses with a logical AND.
  • $or: Joins query clauses with a logical OR.
  • $not: Inverts the effect of a query expression.
  • $nor: Joins query clauses with a logical NOR.

If no operator is specified for a value in a query, the $eq operator is assumed. For example, the query {"name": "Alice"} is equivalent to {"name": {"$eq": "Alice"}}. Logical operators only support two operands. To combine more than two operands, you can nest logical operators.

Here are some examples of queries:

  • Fetch documents where the name field is equal to "Alice": {"name": "Alice"}
  • Fetch documents where the age field is greater than 18: {"age": {"$gt": 18}}
  • Fetch documents where the name field is equal to "Alice" and the age field is greater than 18: {"$and": [{"name": "Alice"}, {"age": {"$gt": 18}}]}
  • Fetch documents where the name field is equal to "Alice" or the age field is greater than 18: {"$or": [{"name": "Alice"}, {"age": {"$gt": 18}}]}
  • Fetch documents where the name field is not equal to "Alice": {"name": {"$ne": "Alice"}}
  • Fetch documents where the name field does not exist: {"name": {"$exists": false}}
  • Fetch documents where the name field matches the regular expression /^A/: {"name": {"$regex": "^A"}}