How to create an alias from an select result in oracle? - oracle

Question

I want to create an alias from an select result.I've tried to use oracle dynamic query but doesn't working.Here is my sql:
declare
v_a varchar2(50);
sql_smt varchar2(200);
begin
select TO_CHAR('#'||TO_CHAR(sysdate-30,'yyyymmdd')||'-'||TO_CHAR(sysdate+2,'yyyymmdd')) INTO v_a from dual;
sql_smt :='SELECT sysdate as :1 FROM dual';
execute immediate sql_smt using v_a;
end;
I want to reach to an result like in the photo.
Thanks for any help!

Answer 1

As you've tagged this for SQL Developer you could use (ab)use substitution variables for this; in your worksheet do:
column x_title new_value y_title noprint;
select TO_CHAR('#'||TO_CHAR(sysdate-30,'yyyymmdd')||'-'||TO_CHAR(sysdate+2,'yyyymmdd'))
as x_title
from dual;
set verify off
select sysdate as "&y_title" from dual;
which when you run as a script (F5) produces this in the Script Output window:
<blank lines ...>
#20190126-
----------
2019-02-25
and then if you run the last line again as a statement (control-enter) the Query Result window shows it as you wanted, from the image in your question.
You could also use the column command which makes the output in the Script Output closer to what you wanted when run as a script:
column sysdate heading &y_title
select sysdate from dual;
#20190126-20190227
------------------
2019-02-25
but then when run as a statement the Query Results window doesn't honour that heading.
Note that this is all client-specific functionality, not SQL - it will work in SQL Developer, and the script versions will work in SQL*Plus and SQLcl, but not in other clients (unless they have tried to feature-match SQL*Plus to some extent).
If you aren't only going to be viewing the results in one of those clients but actually want to end up, say, pulling them into an application over JDBC or whatever, then other solutions would be more appropriate. Generating a ref cursor with the column as the name you want would be fairly simple. But that's not what you've asked for...
OK, since you asked in a comment, you can open a ref cursor in an anonymous block:
var rc refcursor
declare
l_alias varchar2(50);
begin
select TO_CHAR('#'||TO_CHAR(sysdate-30,'yyyymmdd')||'-'||TO_CHAR(sysdate+2,'yyyymmdd'))
into l_alias
from dual;
open :rc for 'SELECT sysdate as "' || l_alias || '" FROM dual';
end;
/
PL/SQL procedure successfully completed.
print rc
#20190127-
----------
2019-02-26
or without the local variable:
var rc refcursor
begin
open :rc for 'SELECT sysdate as "'
|| TO_CHAR('#'||TO_CHAR(sysdate-30,'yyyymmdd')||'-'||TO_CHAR(sysdate+2,'yyyymmdd'))
|| '" FROM dual';
end;
/
PL/SQL procedure successfully completed.
print rc;
#20190127-
----------
2019-02-26
Again var[iable] and print are client-specific commands; and I don't think there's a way to get the results in the Query Results grid with this approach. But you can use the same anonymous block approach from other clients or applications; e.g. from JDBC you could have a statement as:
String sql = "begin open ? for 'SELECT sysdate as \"'"
+ "|| TO_CHAR('#'||TO_CHAR(sysdate-30,'yyyymmdd')||'-'||TO_CHAR(sysdate+2,'yyyymmdd'))"
+ "|| '\" FROM dual'; end;";
and then bind the ? parameter placeholder as a cursor type before executing. That probably isn't very useful though as you'd have to examine the metadata to find the column alias anyway, and you could generate it on the application side using the application language tools (e..g Java date manipulation).
You could also create a function that returns a ref cursor, which you could then call from a plain query (instead of an anonymous block), which would allow you to see it in the Query Results grid - possibly with an extra step to show the cursor result. But you made not need that extra level of code or want another object to be created in your DB.

Answer 2

Would something like this work?
declare
col_hdr varchar2(50);
sys_date varchar2(26);
sql_smt varchar2(200);
begin
select TO_CHAR('#'||TO_CHAR(sysdate-30,'yyyymmdd')||'-'||TO_CHAR(sysdate+2,'yyyymmdd')) INTO col_hdr from dual;
sql_smt :='SELECT sysdate ' || ' as "' || col_hdr || '" FROM dual';
dbms_output.put_line(sql_smt);
execute immediate sql_smt into sys_date;
dbms_output.put_line('done');
end;