Oracle SQL - If Exists, Drop Table & Create - sql

Question

Can some one please guide me what's wrong with this query? In SQL Server we just check the presence of the Object_ID of a table to drop it and re-create it. I am new to Oracle and wrote this query:
declare Table_exists INTEGER;
BEGIN
Select count(*) into Table_exists from sys.all_tables where table_name='TABLENAME1';
EXCEPTION
WHEN NO_DATA_FOUND
THEN
Table_Exists :=0;
if(table_exists)=1
Then
Execute Immediate 'Drop Table TABLENAME1;'
'Create Table TABLENAME1;';
DBMS_OUTPUT.PUT_LINE('Table Dropped and Re-Created!');
Else
Execute Immediate 'Create Table TABLENAME1;';
DBMS_OUTPUT.PUT_LINE('New Table Created!');
END IF;
END;
I get the output - ANONYMOUS BLOCK COMPLETED, but the table is not created. The table was previously existing, so I dropped it to check if the PL/SQL is actually creating the table, but NO. What is wrong here? What am I missing? Please guide.

Answer 1

When you are using all_tables filter the results for your
schema by adding where owner = 'your_schema'
or use sys.user_tables
ALL_TABLES describes the relational tables accessible to the current user
USER_TABLES describes the relational tables owned by the current user.
When use execute_emmidiate remove the ; from the query;
Modified query;
DECLARE
Table_exists INTEGER;
BEGIN
Select count(*) into Table_exists from sys.user_tables where table_name='TABLENAME1';
--or
--Select count(*) into Table_exists from sys.all_tables
--where table_name='TABLENAME1' and owner = 'your_DB';
if table_exists = 1 Then
Execute Immediate 'Drop Table TABLENAME1';
Execute Immediate 'Create Table TABLENAME1(num number)';
DBMS_OUTPUT.PUT_LINE('Table Dropped and Re-Created!');
Else
Execute Immediate 'Create Table TABLENAME1(num number)';
DBMS_OUTPUT.PUT_LINE('New Table Created!');
END IF;
END;

Answer 2

First note:
Select count(*) into Table_exists
from sys.all_tables
where table_name = 'TABLENAME1';
will always return one row. You don't need the exception handling.
My best guess is that you have more than one table called TABLENAME1. Run this query to find out:
Select *
from sys.all_tables
where table_name = 'TABLENAME1';
Oracle stores tables from all owners that you can access. You might also want to check OWNER_NAME in the where clause.
However, you seem to understand exception handling. So, just drop the table, ignore any errors, and then recreate the table.

Answer 3

The EXCEPTION clause lasts till the next END and not just the next statement. If you want to continue after catching the exception you need to add an additional BEGIN/END:
declare
Table_exists INTEGER;
BEGIN
BEGIN
Select count(*) into Table_exists from sys.all_tables where table_name='TABLENAME1';
EXCEPTION
WHEN NO_DATA_FOUND THEN
Table_Exists :=0;
END;
if(table_exists)=1 Then
Execute Immediate 'Drop Table TABLENAME1;'
Execute Immediate 'Create Table TABLENAME1;';
DBMS_OUTPUT.PUT_LINE('Table Dropped and Re-Created!');
Else
Execute Immediate 'Create Table TABLENAME1;';
DBMS_OUTPUT.PUT_LINE('New Table Created!');
END IF;
END;
As pointed out by Gordon, the EXCEPTION clause is not really needed in this case since count(*) will always return one row. So the following is sufficient:
declare
Table_exists INTEGER;
BEGIN
Select count(*) into Table_exists from sys.all_tables where table_name='TABLENAME1';
if(table_exists)=1 Then
Execute Immediate 'Drop Table TABLENAME1;'
Execute Immediate 'Create Table TABLENAME1;';
DBMS_OUTPUT.PUT_LINE('Table Dropped and Re-Created!');
Else
Execute Immediate 'Create Table TABLENAME1;';
DBMS_OUTPUT.PUT_LINE('New Table Created!');
END IF;
END;