How can I sort by a table column in varying cases (Oracle)

Question

How can I sort a table with a column of varchar2 with characters in varying cases (UPPER and lower)?

For example, when I do an order by

Answer 1

If you're on relatively recent versions of Oracle, you should look at setting NLS_SORT/NLS_COMP, rather than using the LOWER() function.

If you don't want to globally affect the instance, you can use the NLSSORT() function to set the NLS_SORT for the scope of a specific query.

SQL> create table case_insensitive(a varchar2(10));

Table created.

SQL> insert into case_insensitive values('D');

1 row created.

SQL> 
SQL> 
SQL> c/'D/'c
  1* insert into case_insensitive values('c')
SQL> /

1 row created.

SQL> c/'c/'B
  1* insert into case_insensitive values('B')
SQL> /

1 row created.

SQL> c/'B/'a
  1* insert into case_insensitive values('a')
SQL> /

1 row created.

SQL> commit;

Commit complete.

SQL> select * from case_insensitive;

A
----------
D
c
B
a

SQL> select * from case_insensitive order by a;

A
----------
B
D
a
c

SQL> select * from case_insensitive order by nlssort(a,'NLS_SORT=BINARY_CI'); 

A
----------
a
B
c
D

A good example of this can be found here.