[Solved] Given a table orders with a JSON column details containing {"item":"book","qty":3}, what will this query return?SELECT details->>'item' FROM orders WHERE details->>'qty' = '3'; | PostgreSQL

PostgreSQL - JSON and JSONB

Given a table orders with a JSON column details containing {"item":"book","qty":3}, what will this query return?
SELECT details->>'item' FROM orders WHERE details->>'qty' = '3';

AReturns 'book' for rows where qty is 3.

BReturns NULL for all rows.

CReturns an error due to wrong operator.

DReturns '3' for all rows.

Step-by-Step Solution

Solution:

Step 1: Understand JSON operators used
details->>'item' extracts text value of 'item'; details->>'qty' extracts text value of 'qty'.
Step 2: Analyze WHERE clause condition
WHERE details->>'qty' = '3' filters rows where qty equals string '3'.
Final Answer:
Returns 'book' for rows where qty is 3. -> Option A
Quick Check:
JSON text extraction and filtering works = returns matching rows [OK]

Quick Trick: Filter JSON text values with ->> operator in WHERE clause [OK]

Common Mistakes:

Expecting numeric comparison without quotes
Using -> instead of ->> for text extraction
Assuming query returns error

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Given a table orders with a JSON column details containing {"item":"book","qty":3}, what will this query return?

Step 1: Understand JSON operators used

Step 2: Analyze WHERE clause condition

Final Answer:

Quick Check:

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