As for my reference later, here is the connection string.

(DESCRIPTION_LIST=
(FAILOVER=true)
(LOAD_BALANCE=true)
(DESCRIPTION=
(ADDRESS= (PROTOCOL=TCP) (HOST=server1) (PORT=1521))
(CONNECT_DATA=
(SERVICE_NAME=orcl))
)
(DESCRIPTION=
(ADDRESS= (PROTOCOL=TCP) (HOST=server2) (PORT=1521))
(CONNECT_DATA=
(SERVICE_NAME=orcl))
)
)

JDBC URL will be something like this

jdbc:oracle:thin:@(DESCRIPTION_LIST…)

Googling give me for below solution. And here I post for my future reference, and also for you if you got this same problem .

Run this command first in console.

sqlplus /nolog

And after that, use these commands :

SQL> connect / as sysdba
Connected.
SQL> shutdown abort
ORACLE instance shut down
SQL> startup nomount
ORACLE instance started.
SQL> alter database mount;
SQL> alter database open;

If you got below error

ERROR at line 1:
ORA-01113: file 14 needs media recovery
ORA-01110: data file 14:
‘C:\APP\ADMINISTRATOR\ORADATA\EKPTGHQ1\DATAFILE\IDX02.DBF’

SQL> alter database recover datafile 14 ;

repeat recover datafile step if you have a few corrupted data file.

SQL> shutdown

SQL> startup

That is. Till then…

Happy SQL-ing…

DROP TABLE IF EXISTS MyTable

In Oracle, you can’t do that.

Solution that I found is to create a procedure and execute it.

As for my reference and others (if any) here is the script to create that procedure.

create or replace procedure drop_table (tab_name in varchar2)
is
qry_string varchar2(4000);
cnt number;
begin
select count(1) into cnt from user_tables where lower(table_name) = lower(tab_name);

if cnt > 0 then
qry_string := 'DROP TABLE ' || tab_name;
begin
EXECUTE IMMEDIATE qry_string;
exception
when others then
dbms_output.put_line('Error occured while dropping ' || sqlerrm);
end;
else
dbms_output.put_line('TABLE ' || tab_name ||' does not exist');
end if;
end;

to drop your table, just execute this statement.
exec drop_table(‘MyTable’);

So, you can safely execute below statement without error if the table is not exist.
exec drop_table(‘MyTable’);
create table MyTable as select * from MyOtherTable;

I then look at the Event Viewer logs and give me another error message.

ACTION : ‘CONNECT’ DATABASE USER: ‘/’ PRIVILEGE : SYSDBA CLIENT USER: NT AUTHORITY\SYSTEM CLIENT TERMINAL: MYAREJAE STATUS: 0 .

Googling around give me below solution. Just run the command and everything goes back to normal.

oradim -edit -sid orcl -startmode auto

Depending on the situation, I think maybe this solution is not necessary true for everyone but at least it works for me.

Till then…

Happy Coding…

ISNULL(myField,0)

In Oracle, you can use NVL to get the same result.

NVL(myField,0)

Same thing for MySQL, you can use IFNULL to get the same result.

IFNULL(myField,0)

Don’t under estimate with this function. I’m debugging my program for almost 1 hours just to notice that some values in my Oracle tables having NULL values and causing errors while inserting to MySQL tables.

That’s my quick update for today. Till then…Happy Coding.