Cursor with parameters in PL/SQL

Ver este post em Portugûes

Here I'm gonna show another technique to work with cursors in PL/SQL. I had to do something at work where it was very useful: cursor that take arguments.

The biggest advantages of parametrized queries is that the server doesn't have to pass through the parse and plan phases ever again (after the first time, of course) and the compile-time checking for syntax errors (when we use string queries we only know any syntax errors in runtime).

That said let's go to examples:

cursor ProductCursor(pname in varchar2) is
    select *
    from product
    where name like pname;

Nice, isn't it? It's like a procedure in terms of syntax. And opening the cursor is like this:

open ProductCursor('A%');

It'll open the cursor with all the products which name starts with 'A'.

We can create a rowtype based var from this cursor:

prod ProductCursor%rowtype;

Now I'm gonna join it all in a script:

declare
    -- Cursor
    cursor ProductCursor(pname in varchar2) is
        select *
        from product
        where name like pname;

    -- Simple loop
    prod ProductCursor%rowtype;

    -- bulk collect loop
    type Tprods is table of ProductCursor%rowtype;
    prods Tprods;
    i integer;

begin
    -- simple loop
    open ProductCursor('A%');
    loop
        fetch ProductCursor into prod;
        exit when ProductCursor%notfound;
        DBMS_OUTPUT.put_line(prod.nome);
        -- other commands
    end loop;
    close ProductCursor;

    -- bulk collect loop
    open ProductCursor('A%');
    fetch ProductCursor bulk collect into prods;
    for i in prods.first .. prods.last loop
        DBMS_OUTPUT.put_line(prods(i).nome);
        -- another commands using prods(i)
    end loop;
    close ProductCursor;
end;

Cool, isn't it? See you next time.