trouble creating headers using spool in sqlplus

问题

I have a lot of data that I want to spool to a csv file. I need to set heading off so the heading will not repeat every page. However, I still need my produced file to contain headers. Is there a way to add a row of headers (not to the table itself) into the query that won't actually be considered a header when spooling? This is my code which works, it just doesn't contain headers when I set heading off.

 select a.col1 as name1, 
        a.col2 as name2, 
        b.col3 as name3
from tab1 a, 
     tab2 b

Thanks in advance

回答1:

you could always try something like:

set heading off;

select 'NAME1' name1, 'NAME2' name2, 'NAME3' name3 from dual
union all
select a.col1 as name1, a.col2 as name2, b.col3 as name3
from tab1 a, tab2 b
where <join condition>;

ETA: If the column types returned by the main query aren't all strings, you'll have to explicitly convert them. Here is an example:

create table test1 (col1 number,
                    col2 date,
                    col3 varchar2(10),
                    col4 clob);

insert into test1 values (1, sysdate, 'hello', 'hello');

commit;

select 'col1' col1, 'col2' col2, 'col3' col3, 'col4' col4 from dual
union all
select col1, col2, col3, col4
from   test1;
       *
Error at line 1
ORA-01790: expression must have same datatype as corresponding expression

set heading off;

select 'col1' col1, 'col2' col2, 'col3' col3, to_clob('col4') col4 from dual
union all
select to_char(col1), to_char(col2, 'dd/mm/yyyy hh24:mi:ss'), col3, col4
from   test1;

col1                                     col2                col3       col4    
1                                        05/08/2015 11:23:15 hello      hello

回答2:

You said you're spooling to a CSV file, so presumably the column spacing doesn't matter (and you have set colsep , already).

If so, you can use the SQL*Plus prompt command to fake a header, without needing a union:

prompt name1,name2,name3

 select a.col1, 
        a.col2, 
        b.col3
from tab1 a, 
     tab2 b

Or a separate query, again without the union:

set feedback off
 select 'name1', 'name2', 'name3' from dual;
set feedback on -- optionally; probably not in this case

 select a.col1, 
        a.col2, 
        b.col3
from tab1 a, 
     tab2 b

Again the values won't align with the real data columns, but for CSV you don't really care. (For CSV I usually explicitly concatenate the values with commas anyway, which removes a load of whitespace and makes the file smaller).