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Query operators

Comparison, set membership, and boolean logic inside a filter.

By the end: Express any single-collection condition without writing a loop.

1. Comparison operators

   MongoDB comparison operators: $gt, $gte, $lt, $lte, $ne and how to combine two of them on a single field.

2. $in and $nin

   MongoDB $in and $nin: match a field against a list of acceptable values, and the trap $nin sets with missing fields.

3. Logical operators and implicit AND

   MongoDB $and, $or and $not, plus the implicit AND that makes an explicit $and unnecessary most of the time.

• Range query
• $in
• Implicit AND wrapping an $or