VARIADIC parameters in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the VARIADIC keyword do in PostgreSQL functions?

VARIADIC allows a function to accept a variable number of arguments as an array, letting you pass many values without specifying each one separately.

beginner

How do you declare a VARIADIC parameter in a PostgreSQL function?

You add the keyword VARIADIC before the last parameter's type, for example: VARIADIC integer[]. This means the function can take many integers as separate arguments.

intermediate

Can a PostgreSQL function have more than one VARIADIC parameter?

No, a function can have only one VARIADIC parameter, and it must be the last parameter in the function's argument list.

beginner

How do you call a function with a VARIADIC parameter?

You can pass multiple arguments directly, or pass an array with the VARIADIC keyword before it. For example: SELECT func(1, 2, 3) or SELECT func(VARIADIC ARRAY[1,2,3]).

intermediate

Why use VARIADIC parameters instead of arrays in PostgreSQL functions?

VARIADIC parameters let you write cleaner calls by passing multiple values directly without manually creating an array, making the function easier to use.

What is the purpose of the VARIADIC keyword in PostgreSQL functions?

A To declare a function as recursive

B To optimize query performance

C To specify the return type of a function

D To allow a function to accept a variable number of arguments

VARIADIC lets a function accept many arguments as an array, enabling flexible input.

How many VARIADIC parameters can a PostgreSQL function have?

A None, VARIADIC is not allowed in PostgreSQL

B Multiple, anywhere in the parameter list

C One, and it must be the last parameter

D Two, but only if they are arrays

Only one VARIADIC parameter is allowed and it must be last.

Which of these is a valid way to call a function with a VARIADIC parameter?

A SELECT func(1, 2, 3);

B SELECT func(ARRAY[1, 2, 3]);

C SELECT func(VARIADIC 1, 2, 3);

D SELECT func(1; 2; 3);

You can pass multiple arguments directly without ARRAY keyword.

What type must a VARIADIC parameter be declared as?

A An array type, like integer[]

B A scalar type, like integer

C A composite type

D Any type except arrays

VARIADIC parameters must be declared as arrays.

Why might you prefer VARIADIC parameters over passing an array directly?

A Because VARIADIC improves query speed

B Because VARIADIC lets you pass multiple values without creating an array manually

C Because VARIADIC parameters can be anywhere in the parameter list

D Because VARIADIC parameters can return multiple values

VARIADIC simplifies function calls by allowing multiple separate arguments.

Explain how VARIADIC parameters work in PostgreSQL functions and how to use them in function calls.

Think about how you can pass many values without making an array yourself.

Describe the rules and limitations of using VARIADIC parameters in PostgreSQL functions.

Focus on placement, count, and type of VARIADIC parameters.