Oracle 21c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE table_name (project, value) AS
SELECT 'a', 0.00 FROM DUAL UNION ALL
SELECT 'b', 0.42 FROM DUAL UNION ALL
SELECT 'c', 1.00 FROM DUAL;
3 rows affected

SELECT project, 
       TO_CHAR(CUSTOMIZED_VALUE, 'FM990') || '%' AS percentage 
FROM (
  SELECT t.*,
         100 - round(value, 5) * 100 AS customized_value
  FROM   table_name t
);


PROJECT
PERCENTAGE


a
100%

b
58%

c
0%


WITH subquery_factoring_clause (project, value, customized_value) AS (
  SELECT t.*,
         100 - round(value, 5) * 100 AS customized_value
  FROM   table_name t
)
SELECT project, 
       TO_CHAR(CUSTOMIZED_VALUE, 'FM990') || '%' AS percentage 
FROM   subquery_factoring_clause;


PROJECT
PERCENTAGE


a
100%

b
58%

c
0%


SELECT project, 
( CASE 
WHEN TO_CHAR(100 - round(value, 5) * 100) NOT LIKE '.%' 
THEN (100 - round(value, 5) * 100) || '%'
ELSE '0' || (100 - round(value, 5) * 100) || '%' 
END ) AS percentage 
FROM table_name;


PROJECT
PERCENTAGE


a
100%

b
58%

c
0%