Get a Column value based on other column value in a single query

Question

Hi All,
I have a problem here -
In Table XYZ I have columns by name A, B, C and COL_I. COL_I has a value A or B or C. Based on the value in COL_I, I need to get the value from the corresponding column in the table.
For Ex: If the COL_I has the value as 'A' then I need to fetch the value from the column A. If it is 'B' then fetch from column B.
This has to be done in a single query.
Thanks,
san_mah

Answer 1

Hi You can use this query
I have taken this simple case
SQL> desc column_fetch
Name Null? Type
C_FIRST_NAME VARCHAR2(30)
C_MIDDLE_NAME VARCHAR2(30)
C_LAST_NAME VARCHAR2(30)
C_GET_NAME VARCHAR2(30)
based on C_GET_NAME find values in columns C_FIRST_NAME,C_MIDDLE_NAME,C_LAST_NAME
Values in Table
SQL> select * from column_fetch
2 ;
C_FIRST_NAME C_MIDDLE_NAME C_LAST_NAME C_GET_NAME
A B C D
A B C F
A B C F
A B C A
A B C B
A B C C
CASE Statement:
SELECT
CASE WHEN c_first_name=c_get_name THEN c_first_name
WHEN C_MIDDLE_NAME=C_GET_NAME THEN C_MIDDLE_NAME
WHEN C_LAST_NAME=C_GET_NAME THEN C_LAST_NAME
ELSE 'Nothing' END
FROM column_fetch;