pl / sql中的过程中的多个/嵌套的开始/结束，函数语句

Question

i´m new to PL/SQL and don´t know how to write it clean and with good practice. I read and watched a view tutorials but these examples were much easyier than my procedure. To create a "large" readable, clean procedure i would use multiple and/or nested begin/ends and functions like this:

begin statement... function... end function exception end

begin.... and so on

but i´m not sure if this is a lean way to write PL/SQL. I need multiple selects on different tables, find rows use them and isert and update rows in different tables. All that in a single procedure. In general i would use begin/end for new Statements, declares for just locally used variables and functions for operations on the result of a statement. Would this be good practice?

Thanks for your help

Answer 1

begin...end; alone does nothing. You only need a nested block if it has a declare or exception that makes sense at that level.

For example, the inner begin / end keywords here are pointless, and you can just remove them:

begin
    ...

    begin
        processing steps
    end;

    ...
end;

A nested block is useful if we want to handle some exception in a nested block only (for example, handle no_data_found exceptions for a particular lookup, or file operations for utl_file ). This is often better than having exception handlers at the end, especially for procedures with a lot of processing steps:

begin
    ...

    begin
        processing steps
    exception
        when no_data_found then...
    end;

    ...
end;

Similarly, we might declare a local variable or constant etc with the scope of the nested block only. This is probably a less usual requirement than the exception example, but there are cases where it could be useful:

begin
    ...

    declare
        x constant integer := whatever();
    begin
        processing steps using x
    end;

    ...
end;

If the procedure is complex with a large number of steps, you might consider ways to break it up into smaller reusable modules.