Reg: Nullable column search

Question

Hi all,
I have a table DIAGNOSIS which has a QDESC as a nullable column.
columns DIAGCODE and SDESC are not nullable.
I have written a Stored Procedure to retrieve records from DIAGNOSIS table based on the columns values specified.
p_<column_name> indicates the parameter passed to the Stored Procedure
The correspong SQL statement goes as follows.
SELECT * FROM DIAGNOSIS
WHERE
UPPER(DIAGCODE) LIKE
(CASE WHEN LENGTH(p_DIAGCODE) > 0 THEN '%' || UPPER(p_DIAGCODE) || '%' ELSE '%' END)
AND UPPER(SDESC) LIKE
(CASE WHEN LENGTH(p_SDESC) > 0 THEN '%' || UPPER(p_SDESC) || '%' ELSE '%' END)
-- QDESC is a nullable field; but the following logic doesnt work :-(
AND UPPER(QDESC) LIKE
(CASE WHEN LENGTH(p_QDESC) > 0 THEN '%' || UPPER(p_QDESC) || '%' ELSE '%' END)
Sample data of the table is as follows.
DIAGCODE SDESC QDESC
123 DESC 1 AAA
123 DESC 2
123 DESC 3 BBB
123 DESC 4
When I use the above query to find records with DIAGCODE as 123, I get
DIAGCODE SDESC QDESC
123 DESC 1 AAA
123 DESC 3 BBB
i.e QDESC with null values are not displayed.
How am I supposed to modify the query to get the correct result?
Any help would be highly appreciated.
Thanks n Regards,
Tanuja

Answer 1

Let's assume the formal parameter is called p_column_name.
The actual content of that parameter is 'DIAGCODE' or 'Q_DESC' or whatever.
In static sql
you can only have
&lt;column_name&gt; = &lt;constant&gt;
and &lt;constant&gt; can be replaced by a bind variable.
This construct
select *
from &lt;table&gt;
where p_column_name is null
is not going to work, as there is no p_column_name in that table.
This construct
declare
dynstr varchar2(100);
p_dummy varchar2(100);
p_column_name varchar2(30);
begin
p_column_name := 'bar';
dynstr := 'select bar from foo where '||p_column_name||' is null';
execute immediate dynstr into p_dummy;
end;
although silly dummy code is going to work.
Hth
Sybrand Bakker
Senior Oracle DBA