Arrow operators (-> and ->>) in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the PostgreSQL arrow operator -> do when used with JSON data?

The -> operator extracts a JSON object field by key and returns it as JSON, preserving the JSON format.

beginner

How is the ->> operator different from -> in PostgreSQL JSON queries?

The ->> operator extracts a JSON object field by key and returns the value as text, not as JSON.

beginner

Given a JSON column data with value {"name": "Alice", "age": 30}, what does data->'name' return?

It returns the JSON string "Alice" including the quotes, because it returns JSON format.

beginner

Given the same JSON column data, what does data->>'name' return?

It returns the text Alice without quotes, because it returns the value as plain text.

intermediate

Can the arrow operators -> and ->> be used to access elements inside JSON arrays in PostgreSQL?

Yes, you can use -> with an integer index to get a JSON element from an array, and ->> to get it as text.

What type of value does the PostgreSQL operator -> return when extracting a JSON field?

A JSON value

B Text value

C Integer value

D Boolean value

The -> operator returns the extracted field as JSON, preserving its JSON format.

Which operator would you use to get a JSON field value as plain text in PostgreSQL?

A ->>

B @>

C #>

D ->

The ->> operator extracts the JSON field and returns it as text.

If data is a JSON column with {"age": 25}, what does data->>'age' return?

A Number 25

B "25"

C Text 25

D 25

The ->> operator returns the value as text without quotes, so it returns the string '25'.

Can you use the arrow operators to access elements inside a JSON array by index?

A Only with -> but not ->>

B No, arrow operators only work with object keys

C Yes, using an integer index with -> or ->>

D Only with ->> but not ->

You can use -> or ->> with an integer index to access JSON array elements.

What will data->'missing_key' return if the key does not exist in the JSON object?

A Empty string

B NULL

C Error

D Zero

If the key is missing, the operator returns NULL.

Explain how the PostgreSQL arrow operators -> and ->> differ when extracting data from JSON columns.

Think about the data type returned and how you might use the result.

Describe how to access an element inside a JSON array stored in a PostgreSQL column using arrow operators.

Remember arrays use numbers as keys.