Edit

ORA-00998: must name this expression with a column alias

Note:
Error may occur when used CTAS or CREATE VIEW

SQL>
CREATE OR REPLACE VIEW function_view AS
SELECT UPPER(ename), LOWER(job), deptno
FROM scott.emp;

*
ERROR at line 2:
ORA-00998: must name this expression with a column alias

-- alias the columns
-- fixed by

CREATE OR REPLACE VIEW scott.function_view AS
SELECT UPPER(ename) AS ENAME, LOWER(job) AS JOB, deptno
FROM scott.emp;

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