Comparison operators (==, <, >, >=, <=) in Firebase - Step-by-Step Execution

Process Flow - Comparison operators (==, <, >, >=, <=)

Start Comparison

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Evaluate Left Value

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Evaluate Right Value

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Apply Operator (==, <, >, >=, <=)

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Result: True or False

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Use Result in Query or Condition

Comparison operators check two values and return true or false, which helps decide what data to fetch or actions to take.

Execution Sample

Firebase

db.collection('users').where('age', '>=', 18).get()

This query fetches users whose age is 18 or older using the '>=' comparison operator.

Process Table

Step	Left Value	Operator	Right Value	Evaluation	Result
1	age field value (e.g., 20)	>=	18	20 >= 18	True
2	age field value (e.g., 16)	>=	18	16 >= 18	False
3	age field value (e.g., 18)	==	18	18 == 18	True
4	age field value (e.g., 17)	<	18	17 < 18	True
5	age field value (e.g., 19)	<=	18	19 <= 18	False
6	Query applies filter only to documents where result is True

💡 Comparison stops after evaluating each document's field against the operator and value.

Status Tracker

Variable	Start	After Eval 1	After Eval 2	After Eval 3	After Eval 4	After Eval 5	Final
age field value	varies per document	20	16	18	17	19	varies per document

Key Moments - 3 Insights

Why does 'age >= 18' return false for some users?

Because the user's age is less than 18, as shown in execution_table row 2 where 16 >= 18 evaluates to false.

Is '==' the same as '>=' or '<='?

'==' checks if values are exactly equal, while '>=' and '<=' check if values are greater or equal, or less or equal respectively, as shown in rows 3 and 1.

What happens if the field value is missing?

The comparison usually returns false because there is no value to compare, so the document is excluded from results.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result of evaluating age = 17 with operator '<' and right value 18?

A Error

B True

C False

D Undefined

💡 Hint

Check row 4 in the execution_table where 17 < 18 is evaluated.

At which step does the comparison 'age == 18' return true?

A Step 3

B Step 1

C Step 5

D Step 2

💡 Hint

Look at the operator and result columns in execution_table row 3.

If a user's age is 19, what is the result of 'age <= 18' comparison?

A True only if age is 18

B True

C False

D Cannot determine

💡 Hint

Refer to execution_table row 5 where 19 <= 18 is evaluated.

Concept Snapshot

Comparison operators check two values and return true or false.
Operators: == (equal), < (less than), > (greater than), >= (greater or equal), <= (less or equal).
Used in Firebase queries to filter data.
Example: where('age', '>=', 18) fetches users 18 or older.
If comparison is false, document is excluded from results.

Full Transcript

Comparison operators in Firebase compare two values and return true or false. These operators include equal (==), less than (<), greater than (>), greater or equal (>=), and less or equal (<=). When you write a query like where('age', '>=', 18), Firebase checks each document's age field. If the age is 18 or more, the comparison returns true and the document is included. If not, it returns false and the document is excluded. This process repeats for each document in the collection. Understanding these operators helps you filter data effectively in Firebase.