Dynamic queryin based on number of inputs provided

Question

I have 7 columns in a tables for which the user can put in values in the fields in the front end and query. The 7 columns have 7 corresponding fields in the front end. But the querying has to be dynamic ... i.e the user does not have to enter all the items in the front end. He can just enter one column value, or 2 upto 7 values for the different columns and it should pass these values to the back end and query the table based on the user inputs and retrieve the rows.
This means while doin the select on the table the "where" clause where the user provides inputs should be flexible. It should just filter the data based on how many ever input fields the user types in.
Please let me know how I can achieve this.
For Example if the columns are col1,col2,col3 .....col7
If the user just provides value for col1 = col1value and col3 = col3val from front end the query should be like
select * from table where col1= col1value and col3 = col3value
similarly if he just provides col2= col2val and col3 = col3 val then
select * from table where col2= col2value and col3 = col3value
Edited by: user635059 on Dec 15, 2008 4:55 PM

Answer 1

Hi,
I assume only the WHERE-clause changes, depending on the user inputs.
In PL/SQL, put the parts of the that do no change into string variables.
Add lines of the WHERE-caluse as needed.
When you have a complete query in a string, use EXECUTE IMMEDIATE to run it.
For example
before_where_txt  VARCHAR2 (5000) := 'SELECT col_a, col_b, ....';
after_where_txt   VARCHAR2 (5000) := ' ORDER BY col_b, col_c';  -- Note: no semicolon in string
where_txt         VARCHAR2 (5000);
IF  col_a_filter IS NOT NULL
THEN
    where_txt := where_txt || ' AND col_a = ' || col_a_filter;
END IF;
IF  col_b_filter IS NOT NULL
THEN
    where_txt := where_txt || ' AND col_b = ' || col_b_filter;
END IF;
...  -- All the other columns
-- Change the AND at the beginning of where_txt to WHERE
IF  where_txt  IS NOT NULL
THEN
    where_txt := ' WHERE ' || SUBSTR (where_txt, 4);
END IF;
EXECUTE IMMEDIATE before_where_txt
               || where_txt
               || after_where_txt;