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 common solution is based on this logic: replace the search string with an empty string and divide the difference between old and new length by the length of the search string

(CHAR_LENGTH(name) - CHAR_LENGTH(REPLACE(name, 'substring', ''))) 
/ CHAR_LENGTH('substring')

Hence:

UPDATE test."user"
SET result = 
    (CHAR_LENGTH(name) - CHAR_LENGTH(REPLACE(name, 'o', ''))) 
    / CHAR_LENGTH('o');