Counting the number of occurrences of a substring within a string in PostgreSQL

Question

How can I count the number of occurrences of a substring within a string in PostgreSQL?

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Example:

I have a table

CREATE TABLE test.\"use         


        

Answer 1

A Postgres'y way of doing this converts the string to an array and counts the length of the array (and then subtracts 1):

select array_length(string_to_array(name, 'o'), 1) - 1

Note that this works with longer substrings as well.

Hence:

update test."user"
    set result = array_length(string_to_array(name, 'o'), 1) - 1;