ORA-00933 Error for to_char formatting PLSQL - sql

Question

I have the following codes:
IF nvl(p_value, 0) >= 0 THEN
l_currency_prefix := 'scc.currency_prefix_pos';
l_currency_suffix := 'scc.currency_suffix_pos';
ELSE
l_currency_prefix := 'scc.currency_prefix_neg';
l_currency_suffix := 'scc.currency_suffix_neg';
END IF;
l_query := 'SELECT nvl('||l_currency_prefix||', '')'
||'trim(to_char('||p_value||
',scc.currency_format
,'||'NLS_NUMERIC_CHARACTERS=' || 'scc.decimal_group_separator'||'))'
||'nvl('||l_currency_suffix||', '')
FROM gss.gss_currency_locale scc
WHERE scc.country_code =' ||p_country_code||
'AND scc.currency_code ='|| p_currency_code||
'AND rownum=1';
and here is the dbms output for l_query:
SELECT nvl(scc.currency_prefix_pos, ')trim(to_char(10000,scc.currency_format
,NLS_NUMERIC_CHARACTERS=scc.decimal_group_separator))nvl(scc.currency_suffix_pos, ')
FROM gss.gss_currency_locale scc
WHERE scc.country_code =USAND scc.currency_code =USDAND rownum=1
However, it keep showing an ORA-00933 errors.
I debug these piece of code for few hours and could not find where is the errors.
Could some one please provide some advice on this?

Answer 1

Now some of the problems are obvious. You need something like this:
l_query := 'SELECT nvl('||l_currency_prefix||',
||'trim(to_char('||p_value||
',scc.currency_format || ')' ||
FROM gss.gss_currency_locale scc
WHERE scc.country_code = ''' ||p_country_code|| '''' ||
' AND scc.currency_code = '''|| p_currency_code|| '''' ||
' AND rownum=1';
(I'm not sure if that is 100 percent correct.)
Usually, when creating queries this way, I use replace() instead of direct substitution. Something like:
l_query := 'select nvl(#currency_prefix, trim(#p_value, #currency_format))
from . . . ';
l_query := replace(l_query, '#currency_prefix', l_currency_prefix);
l_query := replace(l_query, '#p_value', p_value);
. . .
I find that this approach makes it much easier to maintain the code and to see what it is doing.