Oracle 18c

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CREATE FUNCTION my_custom_function(
  value NUMBER
) RETURN NUMBER
IS
BEGIN
  DBMS_SESSION.SLEEP(5);
  RETURN value;
END;
/
CREATE TABLE my_table (colA, colB) AS
SELECT 1, 2 FROM DUAL;
1 rows affected

CREATE OR REPLACE VIEW my_view AS
SELECT colA, colB, my_custom_function(colA) colC
FROM my_table;
SELECT colA, colB FROM my_view;


COLA
COLB


1
2


--SELECT * FROM my_view;
ORA-00900: invalid SQL statement