Trying to create table using Union All Clause with multiple Select stmts

Question

The purpose of the query is to get the Substring from the value for eg.
if the value is *2 ASA* then it should come as ASA
where as if the value is *1.5 TST* the it sholud come as TST like wise for others too.
I am trying to execute the below written SQL stmt but getting error as:
*"ORA-00998 must name this expression with the column alias 00998.00000 - Must name this expression with the column alias"*
CREATE TABLE TEST_CARE AS
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3), len FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =5
UNION ALL
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3), len FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =7
UNION ALL
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3), len FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =14
UNION ALL
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3),LEN FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =7 AND old_care_lvl ='Regular'
I want to create the table using the above given multiple select using the Union ALL clause but when trying to create run the query getting error as "ORA-00998 must name this expression with the column alias 00998.00000 - Must name this expression with the column alias"
Please guide me how to approach to resolve this problem.
Thanks in advance.

Answer 1

When you create a table using a SELECT statement the column names are derived from the SELECT list.
Your problem is that one of your columns is an expression that does not work as a column name SUBSTR(old_care_lvl,3)What you need to do is alias this expression and the CREATE will pick up the alias as the column name, like this:
CREATE TABLE TEST_CARE AS
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3) column3, len FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =5
UNION ALL
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3), len FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =7
UNION ALL
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3), len FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =14
UNION ALL
SELECT row_id, old_care_lvl,SUBSTR(old_care_lvl,3),LEN FROM test_care_lvl
WHERE LENGTH(old_care_lvl) =7 AND old_care_lvl ='Regular'
);You may not like the name "column3" so use something appropriate.