String to array and array to string in PostgreSQL - Step-by-Step Execution

Concept Flow - String to array and array to string

Start with string

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Use string_to_array()

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Get array output

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Use array_to_string()

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Get string output

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End

Convert a string into an array using string_to_array(), then convert an array back to a string using array_to_string().

Execution Sample

PostgreSQL

SELECT string_to_array('apple,banana,cherry', ',') AS arr;
SELECT array_to_string(ARRAY['apple','banana','cherry'], ',') AS str;

Convert a comma-separated string to an array, then convert an array back to a comma-separated string.

Execution Table

Step	Function Called	Input	Output	Explanation
1	string_to_array	'apple,banana,cherry', ','	{apple,banana,cherry}	Splits string by comma into array elements
2	array_to_string	ARRAY['apple','banana','cherry'], ','	'apple,banana,cherry'	Joins array elements into string separated by comma
3	End	-	-	Conversion complete

💡 All conversions done, no more steps

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
input_string	'apple,banana,cherry'	'apple,banana,cherry'	'apple,banana,cherry'	'apple,banana,cherry'
array_value	NULL	{apple,banana,cherry}	{apple,banana,cherry}	{apple,banana,cherry}
output_string	NULL	NULL	'apple,banana,cherry'	'apple,banana,cherry'

Key Moments - 2 Insights

Why does string_to_array need a delimiter?

string_to_array splits the string at each delimiter to create array elements, so without a delimiter it cannot separate parts (see execution_table step 1).

What happens if array_to_string uses a different delimiter than string_to_array?

The output string will join array elements with the new delimiter, changing the string format (see execution_table step 2).

Visual Quiz - 3 Questions

Look at the execution_table, what is the output of string_to_array at step 1?

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

B {apple,banana,cherry}

C 'apple,banana,cherry'

D NULL

💡 Hint

Check the Output column in execution_table row with Step 1

At which step does the output become a string again?

A Step 2

B Step 1

C Step 3

D Never

💡 Hint

Look at the Output column and Function Called in execution_table

If the delimiter in string_to_array was changed to ';', what would happen?

A The array would split at commas

B The array would be empty

C The array would have one element with the whole string

D The function would error

💡 Hint

string_to_array splits only at the delimiter given (see key_moments about delimiter)

Concept Snapshot

string_to_array(text, delimiter) splits a string into an array by delimiter
array_to_string(array, delimiter) joins array elements into a string
Use matching delimiters for reversible conversion
Useful for parsing CSV-like strings
Both functions are built-in PostgreSQL

Full Transcript

This visual execution shows how PostgreSQL converts a string to an array and back. First, string_to_array splits the input string 'apple,banana,cherry' by commas into an array with three elements. Then, array_to_string joins the array elements back into a single string separated by commas. The variable tracker shows the string and array values at each step. Key moments explain why the delimiter is important for splitting and joining. The quiz tests understanding of outputs at each step and the effect of changing delimiters.