Question

I have this string manipulation

select product,
       CAST((LENGTH(currencies) - LENGTH(REPLACE(currencies, '*', ''))) / LENGTH('*') AS UNSIGNED) AS currencies_count
  from MY_TABLE

to count “currencies” in a single field in this table

product       currencies
-----------   --------------
prod_name_1   *usd*cad*euro*
prod_name_2   *usd*cad*
prod_name_3   *usd*cad*euro*
prod_name_4   
prod_name_5   *usd*

The string manipulation returns a “+1” on all results (for exaple: prod_name_1, 4 currencies instead of 3). This because an external component store checkboxes data in this non-coherent manner (*usd*cad*euro* instead of *usd*cad*euro).

The point is that I can’t change the storage method of this component. There is a way to count the exact number of currencies in a field, ignoring the last “blank” value after the last ‘*’ separator?
How can I modify my string manipulation?

Getting crazy, any help will be very, very appreciated!

Answer 1

The query above is not counting the empty part of the string after the final *. It’s not even splitting it at all. It’s simply saying that:

*eur*usd*

is 3 characters longer than

eurusd

To get the correct value I think you should just check for an empty currencies value, and if found then set the result to 0. Otherwise the result is the number of * symbols minus 1:

SELECT
    CASE WHEN LENGTH(Currencies) = 0 THEN CAST(0 AS UNSIGNED) 
        ELSE CAST((LENGTH(Currencies) - LENGTH(REPLACE(Currencies, '*', ''))) / LENGTH('*') AS UNSIGNED) - 1 END AS currencies_count
FROM MY_TABLE

I don’t have a mysql database to to test that against but it should be OK.