Array data type in PostgreSQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an array data type in PostgreSQL?

An array data type in PostgreSQL allows you to store multiple values of the same type in a single column, like a list inside a table cell.

beginner

How do you declare an integer array column in a PostgreSQL table?

You declare it by specifying the data type followed by square brackets, for example: integer[].

beginner

How can you insert values into an array column in PostgreSQL?

You can insert values using curly braces with comma-separated values, like '{1,2,3}' for an integer array.

intermediate

What function can you use to get the length of an array in PostgreSQL?

You can use the array_length(array, dimension) function, where dimension is usually 1 for one-dimensional arrays.

beginner

How do you access the second element of an array column named tags in PostgreSQL?

Use the syntax tags[2] to get the second element of the array.

Which of the following is the correct way to declare a text array column in PostgreSQL?

A text()

B array[text]

C text[]

D array-text

In PostgreSQL, arrays are declared by adding square brackets after the data type, so text[] is correct.

How do you insert the array {apple, banana, cherry} into a text[] column?

A '{apple,banana,cherry}'

B 'apple,banana,cherry'

C ARRAY['apple','banana','cherry']

D ['apple','banana','cherry']

You insert arrays using curly braces with comma-separated values inside single quotes, like '{apple,banana,cherry}'.

What does the expression array_length(my_array, 1) return?

A The total number of elements in all dimensions

B The length of the first dimension of the array

C The last element of the array

D The number of dimensions of the array

The function array_length returns the size of the specified dimension; 1 means the first dimension.

How do you access the third element of an array column named scores?

A scores[3]

B scores(3)

C scores{3}

D scores->3

PostgreSQL uses square brackets to access array elements, so scores[3] is correct.

Which of these is NOT a valid way to create an array in PostgreSQL?

A ARRAY[1,2,3]

B '{1,2,3}'::integer[]

C SELECT ARRAY(SELECT generate_series(1,3))

D array(1,2,3)

The syntax array(1,2,3) is invalid; arrays are created with ARRAY[...] or using string casts.

Explain how to define and insert data into an array column in PostgreSQL.

Think about how you store lists inside a table cell.

Describe how to access and manipulate elements inside a PostgreSQL array column.

Consider how you get items from a list.