Help needed to create a Procedure

Question

Can anyone help me with a small procedure I have to write?
Requirement to create Stored Procedure :
1.  Create tables
     A1
     A2
     B1
     B2
----------- this is done------
Fill the data in those tables
------------this is also done----
Create "Source_table.tx"t file with table names and place them in any location.
------------this is also done----
write a procedure to read the above file "Source_table.txt"  and it should read the tables name 1 by 1 which performs a simple operation inside SP -->  
Select * from @Table_Name
Also, it should check if the .txt file is exisiting or not.
If exists then Read the file and execute the SP.
      SP does this :
         Select * from A1
         Select * from A2
         Select * from B1
         Select * from B2
After that, write an output file with the counts of records to the same location  where our Source_table.txt exists .
If doesnt exist then write to a .txt file that "File name and Location doesnt exist"

Answer 1

What format is the data inside your .txt file?
If it's just some lines containing the names of the tables then you may as well just use the UTL_FILE package to:
a) check the existence of the file using the UTL_FILE.FGETATTR procedure
b) open and read the contents of the file using the UTL_FILE.FOPEN, UTL_FILE.GET_LINE and UTL_FILE.FCLOSE functions/procedures.
UTL_FILE
Alternatively you could set up an external table to read the .txt file as though it's a table.
Managing External Tables
Once you extract the table names from the .txt file, you'll then have to construct dynamic SQL queries to query the data from them.  Are all of the tables of the same structure or do they change?  If they change you'll have to use the DBMS_SQL package.  If they don't you could do it more statically in PL/SQL code (at least in terms of the structures you're reading the data into), but you may still be better using DBMS_SQL for it.  It depends what you're trying to do exactly and why these table names are being exported to a file and need to be read dynamically in this way.  Often Dynamic coding indicates poor design, but without knowing exactly what you're doing, it's hard to tell if it's really necessary or not.