$lt and $lte for less than in MongoDB - Step-by-Step Execution

Concept Flow - $lt and $lte for less than

Start Query

↓

Check each document

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Compare field value

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$lt: value < target?

Yes→Include document

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Exclude document

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$lte: value <= target?

Yes→Include document

No↓

Exclude document

The query checks each document's field value against a target using $lt (less than) or $lte (less than or equal). Documents passing the test are included in the result.

Execution Sample

MongoDB

db.products.find({ price: { $lt: 50 } })
db.products.find({ price: { $lte: 50 } })

Finds products with price less than 50, and less than or equal to 50 respectively.

Execution Table

Step	Document	price	Condition	Result	Included in Output
1	{_id:1, price:30}	30	30 < 50 ($lt)	True	Yes
2	{_id:2, price:50}	50	50 < 50 ($lt)	False	No
3	{_id:3, price:50}	50	50 <= 50 ($lte)	True	Yes
4	{_id:4, price:60}	60	60 < 50 ($lt)	False	No
5	{_id:4, price:60}	60	60 <= 50 ($lte)	False	No

💡 All documents checked; inclusion depends on $lt or $lte condition result.

Variable Tracker

Variable	Start	After Doc 1	After Doc 2	After Doc 3	After Doc 4	Final
price	N/A	30	50	50	60	60
$lt condition result	N/A	True	False	N/A	False	N/A
$lte condition result	N/A	N/A	N/A	True	False	N/A

Key Moments - 2 Insights

Why does a document with price 50 fail $lt: 50 but pass $lte: 50?

Because $lt means strictly less than 50, so 50 is not less than 50 (false). $lte means less than or equal to 50, so 50 equals 50 (true). See execution_table rows 2 and 3.

Are documents with price greater than 50 ever included?

No, both $lt and $lte exclude values greater than 50. See execution_table rows 4 and 5 where price 60 is excluded.

Visual Quiz - 3 Questions

Look at the execution_table, at step 2, what is the result of the $lt condition for price 50?

A True

B Undefined

C False

D Error

💡 Hint

Check the 'Condition' and 'Result' columns at step 2 in execution_table.

At which step does the $lte condition include a document with price 50?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look for $lte condition results in execution_table rows.

If we change the target value from 50 to 60 in $lt, which document would now be included that was previously excluded?

A Document with price 60

B Document with price 50

C Document with price 30

D No change

💡 Hint

Consider how $lt compares price values to the new target 60.

Concept Snapshot

$lt and $lte operators in MongoDB queries:
- $lt: matches documents where field value is strictly less than target.
- $lte: matches documents where field value is less than or equal to target.
- Used in find queries to filter documents by numeric or date fields.
- Example: { price: { $lt: 50 } } finds documents with price < 50.
- Example: { price: { $lte: 50 } } finds documents with price ≤ 50.

Full Transcript

This visual execution shows how MongoDB's $lt and $lte operators work in queries. The query checks each document's field value against a target number. For $lt, only values strictly less than the target pass. For $lte, values less than or equal to the target pass. The execution table traces documents with prices 30, 50, and 60. Documents with price 30 pass both $lt and $lte conditions. Price 50 fails $lt but passes $lte. Price 60 fails both. The variable tracker shows how price and condition results change per document. Key moments clarify why 50 fails $lt but passes $lte, and why values above target are excluded. The quiz tests understanding of condition results and effects of changing target values. The snapshot summarizes usage and behavior of $lt and $lte in MongoDB queries.