Varchar2

dear all
what the difference betwwen varchar2 and nvarchar2
Best Regards

VARCHAR2 is intended for the characters that are typically used
in the English and other similar languages. NVARCHAR2 is
intended to support the national character set which is used for
some Asian and other languages that require many more
characters. You can find more detailed information in the on-
line Oracle documentation. In the upper right-hand corner of
your screen, you should see an empty box to the right of the
word search. Enter NVARCHAR2 in that box and press your Enter
key. Then when the list of selections appears, scroll down
until you see a topic heading about pl/sql data types, and click
on it.

Similar Messages

Difference between char and varchar, also the difference between varchar2

Hi,
Can anyone explain me the difference between char and varchar, and also the difference between varchar and varchar2...

Varchar2 is variable width character data type, so if you define column with width 20 and insert only one character to tis column only, one character will be stored in database. Char is not variable width so when you define column with width 20 and insert one character to this column it will be right padded with 19 spaces to desired length, so you will store 20 characters in the dattabase (follow the example 1). Varchar data type from Oracle 9i is automaticlly promoted to varchar2 (follow example 2)
Example 1:
SQL> create table tchar(text1 char(10), text2 varchar2(10))
2 /
Table created.
SQL> insert into tchar values('krystian','krystian')
2 /
1 row created.
SQL> select text1, length(text1), text2, length(text2)
2 from tchar
3 /
TEXT1 LENGTH(TEXT1) TEXT2 LENGTH(TEXT2)
krystian 10 krystian 8
Example 2:
create table tvarchar(text varchar(10))
SQL> select table_name,column_name,data_type
2 from user_tab_columns
3 where table_name = 'TVARCHAR'
4 /
TABLE_NAME COLUMN_NAME DATA_TYPE
TVARCHAR TEXT VARCHAR2
Best Regards
Krystian Zieja / mob

On the use of VARCHAR2 vs. CHAR

I'm posting an e-mail thread that has been moving around in my organization, whith guidance from an Oracle representative.
The basic issue concerns the use of CHAR vs. VARCHAR2 when defining a table in Oracle.
I would like to get some comments from the community at large.
1. Business semantics should be represented in every aspect of a database, application, and design as far as I am concerned. Noteably, if the business rule at a corporate entity is clearly stated that when using Oracle the use of CHAR should be limited to those attribute implementations which have the following characteristics; a) The attribute may not be null, b) The attribute must have a character in each of the declared positions.
2. When the Visual Basic application began writing data to the CHAR columns in your application someone should have had a discussion with the developer to find out why this was happening. If the business semantics changed then the logical implemention of the business semantics should have changed as well. That the two were disconnected is not a problem with the CHAR type, it is a problem with the designer or the developer. The bottom line on this instance is that the column should have been defined as a VARCHAR2 data type since the business semantics no longer complied with the criteria set forth in the previous paragraph.
3. I think Oracle trys to load as much of the data from a table or index into shared memory, in this case the database block buffers, as it can in order to facilitate query operations. If Oracle has enough memory and can load a table or index into memory, it will do so. At the same time the database engine will move previously cached data out of memory to accommodate the new requirement.
-----Original Message-----
Thank you for the detail information on CHAR and VARCHAR2. It got me thinking with a DBA hat. I worked as a DBA before and I did use the CHAR type and I will share my experience/thought on CHAR.
I don't like to use the char type like Tom has advised because Oracle does not check to see if the value being inserted fills up the column or not which can lead to a problem. And there is no performance gain or save space in Oracle.
I worked as a DBA before, I used char type on the "must fill/always filled" column (pre DMDC). The application was written in VB with Oracle back end. At some point, VB started inserting values that are short of the column width and created a minor problem (it was supposed to be filled column). The problem was quickly identified and fixed, but it caused an issue.
I realize that I don’t want to define it as a "must fill/always filled" column if you can't enforce it by simply defining the char data type on a table and prevent possible issue in the future.
For a manager, in order to use the char properly, you have to hire client developers with Oracle experience or provide a basic Oracle training in order to avoid the problem I mentioned above in order to use the char type correctly.
I think you, Tom and I are saying the same thing really. Only difference is that Tom and I can not think of a good reason why anyone would like to indicate the business semantics using column type on the database, when it can lead to more work/issues.
In regards to wasted 25 million byes, why would Oracle load the table with 25 million rows? Shouldn't it use an index? Don't you have a serious problem if Oracle is loading table with the 25 million rows?
Just my two cents... : )
-----Original Message-----
May I beg to differ?
CHAR plays a vital role in the intuitive interpretation of a database schema. If designed correctly, the use of CHAR tells anyone who is in the know that this is a must fill column. Thus if a column is defined as CHAR(3) everyone should know that the column will always contain three characters. Defining the column as VARCHAR2(3) does not tell you anything about the data other than that the column may contain 0-3 characters.
Also, If a column is defined as CHAR the column should always be populated. One of the nice features of VARCHAR2 is that if the column is defined at the end of a table, there is no storage overhead until that column is actually populated. Thus if you have a table that has an identifier that is nine characters in length and will always be populated with nine characters, an attribute which describes the type of identifier which is contained in the first column and which must always be populated and is a must fill attribute, and another column which is descriptive and may vary in length or not be populated at time of insert; the following definition does not express the business semantics of the entity:
COL_CD VARCHAR2(9)
COL_TYP_TXT VARCHAR2(26)
COL_TYP_CD VARCHAR2(2)
The above definition also does not take advantage of inherent storage features of Oracle; notably there is a wasted place holder between COL_CD and COL_TYP_TXT and between COL_TYP_TXT and COL_TYP_CD. The next definition does take advantage of the storage features but does not represent the business semantics of the entity:
COL_CD VARCHAR2(9)
COL_TYP_CD VARCHAR2(2)
COL_TYP_TXT VARCHAR2(26)
The above definition does not waste space storing a place holder between COL_TYP_CD and COL_TYP_TXT if the COL_TYP_TXT may be null. The column separator will only be used when the column contains data. The below definition satisfies both the storage and business semantics issues:
COL_CD CHAR(9)
COL_TYP_CD CHAR(2)
COL_TYP_TXT VARCHAR2(26)
This may seem pedantic in nature until you consider the situation where there are 25 million rows in the table represented by the above entity. If each row has a NULL COL_TYP_TXT value then the first example wasted 25 million bytes of storage and 25 million bytes of memory if the full table is loaded into memory. This is an issue which cannot be ignored in high volume databases.
You may wish to know why it is important to define a must fill/always fill column as a CHAR to express the business semantics of an attribute. I can't give a definitive answer to that other than to say that it is just good database manners.
So please, continue to use CHAR when the shoe fits. Don't throw something away that has use just because it is not popular or in the mode.
Also, if I am mistaken in any of the above, please feel free to educate me.
Thanks.
-----Original Message-----
Subject: RE: Oracle on the use of VARCHAR2 vs. CHAR
Ignore if you already got this. This is just FYI.
-----Original Message-----
Below is a detailed answer to your VARCHAR2 or CHAR questions from our Database expert Tom Kyte. The short answer is VARCHAR2 is what you want to use. If you have any questions or want to discuss this in more detail let me know.
A CHAR datatype and VARCHAR2 datatype are stored identically (eg: the word 'WORD' stored in a CHAR(4) and a varchar2(4) consume exactly the same amount of space on disk, both have leading byte counts).
The difference between a CHAR and a VARCHAR is that a CHAR(n) will ALWAYS be N bytes long, it will be blank padded upon insert to ensure this. A varchar2(n) on the other hand will be 1 to N bytes long, it will NOT be blank padded.
Using a CHAR on a varying width field can be a pain due to the search semantics of CHAR.
Consider the following examples:
ops$tkyte@8i> create table t ( x char(10) ); Table created.
ops$tkyte@8i> insert into t values ( 'Hello' );
1 row created.
ops$tkyte@8i> select * from t where x = 'Hello';
X
Hello
ops$tkyte@8i> variable y varchar2(25)
ops$tkyte@8i> exec :y := 'Hello'
PL/SQL procedure successfully completed.
ops$tkyte@8i> select * from t where x = :y; no rows selected
ops$tkyte@8i> select * from t where x = rpad(:y,10);
X
Hello
Notice how when doing the search with a varchar2 variable (almost every tool in the world uses this type), we have to rpad() it to get a hit.
If the field is in fact ALWAYS 10 bytes long, using a CHAR will not hurt -- HOWEVER, it will not help either.
The only time I personally use a CHAR type is for CHAR(1). And that is only because its faster to type char(1) then varchar2(1) -- it offers no advantages.
If you just use varchar2 everywhere, no problem
My advice is, has been, will be very loudly stated as:
IGNORE THE EXISTENCE OF CHAR.
period. If you never use char, you never compare char to varchar2, problem solved.
And if you use char and compare a char(n) to a char(m) they will never compare either.
Just say NO TO CHAR.
**************************************************

Hi,
>>A CHAR datatype and VARCHAR2 datatype are stored identically (eg: the word 'WORD' stored in a CHAR(4) and a varchar2(4) consume exactly the same amount of space on disk, both have leading byte counts).
Ok, but on the other hands:
SGMS@ORACLE10> create table x (name char(10), name2 varchar2(10));
Table created.
SGMS@ORACLE10> insert into x values ('hello','hello');
1 row created.
SGMS@ORACLE10> commit;
Commit complete.
SGMS@ORACLE10> select vsize(name),vsize(name2) from x;
VSIZE(NAME) VSIZE(NAME2)
10 5
SGMS@ORACLE10> select dump(name),dump(name2) from x;
DUMP(NAME) DUMP(NAME2)
Typ=96 Len=10: 104,101,108,108,111,32,32,32,32,32 Typ=1 Len=5: 104,101,108,108,111Cheers

Varchar2 in index vs. number

My indexes on three primary tables total 80gb in space. They have 3-6 columns in the index, one of which is a 10-byte varchar field. This field holds an identifier type in character rather than numeric format. For example, name type is "INDIV" rather than a coded 001. If I use numeric, I will need to decode the text value on my screens/reports.
Is there a cost overhead in using varchar2 rather than number? Is there a space saving in either approach?

U should keep the varchar2 index and make a partition by range or list on it.
At my knowledge, there's no reason to put the key as number as they r no reason to put it as varchar.
If u need the field as a varchar, let it be a varchar... (and in ur example, u will win a decode each time u'll access this key...)
Fred

Convert long to varchar2

Hi there,
I am looking for a convertion, long to varchar2, in a sql statement.
If I run the following query :
select data_default from user_tab_columns
It works fine in sql developper but when I execute it in my PHP code it returns:
Notice: Undefined index: DATA_DEFAULT in /opt/lampp/htdocs/datamodel/index.php on line 64
This issue is due in the case where the columns has null.
So I try with the NVL function:
select nvl(data_default, 'null') from user_tab_columns
ORA-00932: inconsistent datatypes: expected LONG got CHAR
I found on internet some people are using the substr function but it did not working for me.
select substr(data_default, 1, 2000) from user_tab_columns
ORA-00932: inconsistent datatypes: expected NUMBER got LONG
Any one has an idea ?
Regards !

See this thread as well you can get an exaple user function
ORA-00932: inconsistent datatypes
G.

Chnage colum from CLOB to Varchar2 and find the length of CLOB

Hi,
I have got tables contain CLOB fields. I want to converter them to varchar2? Is the a way to do it? how can I find the max of length the data in CLOB fields.
Thanks in advance!!
Michael

Hi All,
Thanks you for your useful information. What I need is to change the colum data type (definaition itself)from CLOB to Varchar2, not just to display the values in CLOB field into varchar2. I have tried to change the date type from COLB to varchar2 in TOAD and got ORA_22859: invaliad modification of columns.
Any suggestions?
Many Thanks
Michael

Need to convert the Varchar2 to decimal

Hi,
I need to convert source sybase varchar2 record in to decimal record in Target DB2 table by using the function in Oracle data integrator.
In my source table, column is defined as varchar2 (4) and in target table same column has defined as Decimal (2). So, is there any function to convert the varchar2 data to decimal record.
thanks,
keshav.

Hi SH,
Thanx so much for your answer!
Well actually I have managed to do the filters, and right now dealing with the convertion of formats.
Right now I am working with Oracle DB 11g, and Excel; and what i would like to do is now that is passing from my uploaded excel the info to my Oracle DB would like to control the ways it pases the info.
Let's say for example, that I have gotten a Field A in my source table (Excel uploaded to ODI), and that on my Orazle Table on Field A i would like to change the data type of the field, or just make sure that the data inserted will always be of certain type? Can I do this with ODI? Could you please give me some advice in how to it? I assume that it should be done on my interface, in the Diagram tab > Target Database > Mapping Area > Implementation Tab > Expression Editor and modify it there, is it?
As this is mapping from excel, can I just use the excel function? it does not make any sense for me as it is all in Oracle. I am sorry but I am kinda confused now.
Once again I do really appreciate your help.

Need to convert varchar2 into decimal

Hi,
I need to convert source sybase varchar2 record in to decimal record in Target DB2 table by using the function in Oracle data integrator.
In my source table, column is defined as varchar2 (4) and in target table same column has defined as Decimal (2). So, is there any function to convert the varchar2 data to decimal record.
thanks,
keshav.

865709 wrote:
Hi,
I need to convert source sybase varchar2 record in to decimal record in Target DB2 table by using the function in Oracle data integrator.You may have more luck in the proper forum
Data Integrator

Need to convert long data type to varchar2

I need to convert a long datatype in an existing table to a
varchar2, in either another table or view. I have a 3rd party
application which needs to query the data in the long data type,
but it can "handle" the long.
What is the best way to do this? I tried to make a trigger, but
I must be missing something. Here is the trigger.
CREATE OR REPLACE TRIGGER "PROD".SV_GET_RTG_COMNT
BEFORE INSERT OR UPDATE ON PROD.RELS_RTG_SEQ_COMNT
FOR EACH ROW
WHEN (OLD.rels_rtg_no = NEW.rels_rtg_no)
DECLARE
-- DECLARE VARIABLES
RTG_COMNT_VAR VARCHAR2(32);
RTG_COMNT_LONG LONG;
BEGIN
Select COMNT_TXT into RTG_COMNT_LONG
from rels_rtg_seq_comnt;
RTG_COMNT_VAR := 'TEXT' || substr(RTG_COMNT_LONG,1,32);
-- If INSERTING
Insert into SV_RTG_SEQ_COMNT (print_cd, comnt_no,
seq_no, rtg_no, comnt_txt) values
(:new.print_cd, :new.comnt_no, :new.seq_no, :new.rels_rtg_no,
rtg_comnt_var);
END;
I tried to use the substr command on the comnt_txt in view but
received an invalid datatype error.
Any help would be greatly appreciated.
Doug

create another table with clob datatype
1)create table clob_tab(pkval number,clob_col clob);
2) insert into clob_tab (select pkval,to_lob(long_col) from
long_tab);
3) use dbms_lob package to do string manipulation using
substr,instr functions on clob column.

Find out varchar2 string NULL columns and Empty columns

Hi dev's ,
my requiremnt is to find out the string columns Names of whose storing NULL values and EMPTY strings. for that i had written below code. it's getting some error.
SET ECHO OFF;
SET FEEDBACK OFF;
SET SERVEROUTPUT ON;
SET VERIFY OFF;
SET PAGES 0;
SET HEAD OFF;
spool D:\stringnull.csv
DECLARE
v_tab_indent NUMBER(5);
v_col_indent NUMBER(5);
v_val1       VARCHAR2(20);
v_val2       VARCHAR2(20);
v_query1     VARCHAR(500);
v_query2     VARCHAR(500);
BEGIN
--DBMS_OUTPUT.ENABLE(100000);
SELECT MAX(LENGTH(table_name))+1,MAX(LENGTH(column_name))    +1
INTO v_tab_indent,v_col_indent
FROM user_tab_columns
WHERE data_type='VARCHAR2';
FOR i IN
(SELECT table_name,
    column_name
FROM user_tab_columns
WHERE data_type IN ('NVARCHAR2', 'CHAR', 'NCHAR', 'VARCHAR2')
ORDER BY table_name,
    column_name
LOOP
    v_query1:='SELECT NVL('||i.column_name||',0) AS VAL
              FROM '||i.table_name||' where '||i.column_name||' IS NULL';
    v_query2:='SELECT '||i.column_name||' AS VAL
              FROM '||i.table_name||' where '||i.column_name||'=''''';
    --dbms_output.put_line(v_query1);
   -- dbms_output.put_line(v_query2);
    EXECUTE immediate v_query1 INTO v_val1;
    EXECUTE immediate v_query2 INTO v_val2;
    dbms_output.put_line (rpad(i.table_name,v_tab_indent,' ')||','||rpad(i.column_name,v_col_indent,' ')||' ,'||v_val1||','||v_val2);
END LOOP;
END;
Spool OFF
Set echo on
Set feedback onERROR:
Error report:
ORA-01403: no data found
ORA-06512: at line 31
01403. 00000 - "no data found"
*Cause:
*Action:
set feedback onpls help me on this issue..
Thanks,

Example:
SQL> DECLARE
2    v_val       VARCHAR2(20);
3    v_query1     VARCHAR(32767);
4 BEGIN
5   FOR i IN (SELECT table_name, column_name FROM user_tab_columns
6             WHERE data_type IN ('NVARCHAR2', 'CHAR', 'NCHAR', 'VARCHAR2')
7             ORDER BY table_name, column_name
8            )
9   LOOP
10     v_query1 := 'SELECT count(*) FROM '||i.table_name||' where '||i.column_name||' IS NULL';
11     EXECUTE immediate v_query1 INTO v_val;
12     dbms_output.put_line(rpad(i.table_name,30,' ')||' : '||rpad(i.column_name,30,' ')||' : '||v_val);
13   END LOOP;
14 END;
15 /
CHILD_TAB                      : DESCRIPTION                    : 0
DEPT                           : DNAME                          : 0
DEPT                           : LOC                            : 0
EMP                            : ENAME                          : 0
EMP                            : JOB                            : 0
MYEMP_OLD                      : ENAME                          : 0
MYEMP_OLD                      : JOB                            : 0
MYNULLS                        : ENAME                          : 0
MYNULLS                        : JOB                            : 4
PARENT_TAB                     : DESCRIPTION                    : 0
T                              : CHAR_VALUE                     : 0
TABLE1                         : COL1_DESC                      : 0
PL/SQL procedure successfully completed.

Custom CAPI service - default value of varchar2 parameter

I have a Custom CAPI Service function. That function has a varchar2 parameter (argument) and I wish to set a default value NULL for that parameter.
I set Default=null, and when I generate CAPI package, my function in that package looks like this (notice the quotation marks around null):
function cs_cjn_prod_cijena
( p_nacin_prodaje in varchar2 default 'null'
return number
is ...
And it should look like this:
function cs_cjn_prod_cijena
( p_nacin_prodaje in varchar2 default null
return number
is ...
I tried setting Default Value Type to Literal, Database Function Call, Client Function Call, but it's always the same thing.
If that parameter was number or date it would generate ok.
It seems like the bug in "Generate CAPI Definition" Headstart Utility.
I know that I can make my function's code to treat the string 'null' as a null default value, but I'd like to have a "real" null as a default value.
Does anybody have a solution for this?
Thanks!
Dalibor

Marcel,
Thank you for your answer, but it didn't help. I have already tried using Database Function Call. This time I tried deleting the CAPI package from repository before generating it again, like you suggested, but it didn't help.
I still get: p_nacin_prodaje in varchar2 default 'null'
Which version of Create CAPI Definition utility do you have?
My version is: HSU_CAPI, Revision: 6.5.2.0 ("Help/About This Utility" in Headstart Utilities application)
Thanks again,
Dalibor

Fill with blanks(spaces) a VARCHAR2 type

Thanks in advance,
I have a VARCHAR2 type rtesta's var of length x(100 char)
how i can fill(write) it without create a other varchar2 var that it'll be only filled with blanks(spaces). e.g
rtesta := ' PC'||fil1||'xxx||fill2....
where fil1 = say 10 spaces.. fill2 = 63 spaces and so on
I would like something as
rtesta := ' PC'|| RPAD(null,10)||'xxx||RPAD(null,63) ...
but.... Oracle treats an empty string as null. And nulls are always a bit special within Oracle. Particularly, rpad('', n) and lpad('', n) returns null.
Exists a built in for my problem?
Thanks

alter table your_table modify(your_column char(100));
update your_table set your_column = ' '
where your_clumn is null; /* (added) But,this is no good for performance */
alter table your_table modify(your_column varchar2(100));Exapmples.
SQL> set null (null)
SQL> create table test (vc varchar2(100));
Table created.
SQL> insert into test values ('');
1 row created.
SQL> insert into test values ('a');
1 row created.
SQL> insert into test values ('abcde');
1 row created.
SQL> select substr(vc,1,10) vc,length(vc) len from test;
VC                          LEN
(null)               (null)
a                             1
abcde                         5
SQL> alter table test modify(vc char(100));
Table altered.
SQL> update test set vc = ' ' where vc is null;
1 row updated.
SQL> alter table test modify(vc varchar2(100));
Table altered.
SQL> select substr(vc,1,10) vc,length(vc) len from test;
VC                          LEN
                            100
a                           100
abcde                       100----
I misread OP's problem, sorry.
Message was edited by:
ushitaki

VARCHAR2:: How to differnciate between NULL and empty string '' ?

Hello to all,
I'm looking for a possibility to differnciate between NULL and empty string '' in column of type VARCHAR2.
I have an application relying on that there is a difference between NULL and ''.
Is it possible to configure ORACLE in some way ?
Thanx in advance,
Thomas

try check if a varchar variable has an empty string
by checking its lengthAnd that would accomplish what? But see for yourself:
DECLARE
v_test VARCHAR2(10);
BEGIN
v_test := '';
DBMS_OUTPUT.put_line(LENGTH(v_test));
v_test := NULL;
DBMS_OUTPUT.put_line(LENGTH(v_test));
END; C.

Insert/update japanese langunage data in a column of datatype varchar2(..)

Hello,
I am using ORACLE DATABASE 11g (EE) and RHEL 5.
I want to insert/update japanese language data in a column which has the datatype as varchar2(256).
I tried to change the NLS_LANGUAGE and NLS_TERRITORY parameters with 'ALTER SESSION set ...' command but no effect.
I tried to bounce back ( shutdown and startup ) the DB but still no effect.
I tried to inset the NLS_LANGUAGE and NLS_TERRITORY in init.ora file but still no use.
If anybody knows the detail steps which i have mentioned above .... let me know. Might be that i am wrong in my method.
Can you please guide me how to change the language of DB for a perticular session to japanese ???
Thanks in advance...
Edited by: VJ4 on May 9, 2011 6:21 PM

VJ4 wrote:
Thanks for the info.
Yes i tried with UNISTR function and was able to insert the data successfully.
but the point is that we can't remember unicode for each of the letter. It's their any method that we can directly insert japanese character using an insert.
As you said :-
Note that changing database character set is something complicated that requires many steps.
Can you please provide me some links or some stuffs to study about the detail steps of chaining database character set.
I have gone through the Oracle online documentation.. if you can pin point any good link in it you can else provide me some other stuff.
Thanks .You will need to convert your database characterset to AL32UTF8. This is not a trivial exercise if your database already has data in it. See these MOS Docs
Changing the NLS_CHARACTERSET to AL32UTF8 / UTF8 (Unicode) (Doc ID 260192.1)
AL32UTF8 / UTF8 (Unicode) Database Character Set Implications (Doc ID 788156.1)
http://download.oracle.com/docs/cd/E11882_01/server.112/e10729/ch11charsetmig.htm#g1011430
HTH
Srini

Varchar2, empty strings and NULL

Hi all,
When inserting an empty string into a column of type varchar2 - is a NULL value stored in the column by the database? I've seen conflicting reports, and I know that the SQL 1992 spec specifies that empty strings not be treated as a NULL value, but that Oracle has traditionally treated zero length strings stored in a varchar2 column as NULL.
So, is there a way to store an empty string in a varchar2 column as an empty string and not a NULL value?
TIA,
Seth

It can be even more complicated or annoying than NULL not equal to ASCII NULL.
example:
create table test_null
(fld1 varchar2(10),
fld2 varchar2(10),
fld3 varchar2(20));
insert into test_null values (chr(0),null, 'chr(0) and null');
insert into test_null values (null, null, 'null and null');
insert into test_null values ('', chr(0), ''''' and chr(0)');
insert into test_null values ('', null, ''''' and null');
select * from test_null;
FLD1       FLD2       FLD3
                      chr(0) and null
                      null and null
                      '' and chr(0)
                      '' and null
1 DECLARE
2 BEGIN
3   for c1 in (select fld1, fld2, fld3 from test_null) loop
4      if c1.fld1 = c1.fld2 then
5         dbms_output.put_line(c1.fld3||' Are equal'||
6                ' Length fld1 = '||to_char(length(c1.fld1))||
7                ' Length fld2 = '||to_char(length(c1.fld2)));
8      else
9         dbms_output.put_line(c1.fld3||' Are NOT equal'||
10                ' Length fld1 = '||to_char(length(c1.fld1))||
11                ' Length fld2 = '||to_char(length(c1.fld2)));
12      end if;
13      dbms_output.put_line(' ');
14   end loop;
15* END;
SQL> /
chr(0) and null Are NOT equal Length fld1 = 1 Length fld2 =
null and null Are NOT equal Length fld1 = Length fld2 =
'' and chr(0) Are NOT equal Length fld1 = Length fld2 = 1
'' and null Are NOT equal Length fld1 = Length fld2 =
PL/SQL procedure successfully completed.

Difference between CHAR and VARCHAR2 datatype

Difference between CHAR and VARCHAR2 datatype
CHAR datatype
If you have an employee name column with size 10; ename CHAR(10) and If a column value 'JOHN' is inserted, 6 empty spaces will be inserted to the right of the value. If this was a VARCHAR column; ename VARCHAR2(10). How would it handle the column value 'JOHN' ?

The CHAR datatype stores fixed-length character strings, and Oracle compares CHAR values using blank-padded comparison semantics.
Where as the VARCHAR2 datatype stores variable-length character strings, and Oracle compares VARCHAR2 values using nonpadded comparison semantics.
This is important when comparing or joining on the columns having these datatypes;
SQL*Plus: Release 10.2.0.1.0 - Production on Pzt Au 6 09:16:45 2007
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SQL> conn hr/hr
Connected.
SQL> set serveroutput on
SQL> DECLARE
2 last_name1 VARCHAR2(10) := 'TONGUC';
3 last_name2 CHAR(10) := 'TONGUC';
4 BEGIN
5 IF last_name1 = last_name2 THEN
6 DBMS_OUTPUT.PUT_LINE ( '-' || last_name1 || '- is equal to -' || last_name2
|| '-');
7 ELSE
8 DBMS_OUTPUT.PUT_LINE ( '-' || last_name1 || '- is NOT equal to -' || last_n
ame2 || '-');
9 END IF;
10 END;
11 /
-TONGUC- is NOT equal to -TONGUC -
PL/SQL procedure successfully completed.
SQL> DECLARE
2 last_name1 CHAR(6) := 'TONGUC';
3 last_name2 CHAR(10) := 'TONGUC';
4 BEGIN
5 IF last_name1 = last_name2 THEN
6 DBMS_OUTPUT.PUT_LINE ( '-' || last_name1 || '- is equal to -' || last_name2
|| '-');
7 ELSE
8 DBMS_OUTPUT.PUT_LINE ( '-' || last_name1 || '- is NOT equal to -' || last_n
ame2 || '-');
9 END IF;
10 END;
11 /
-TONGUC- is equal to -TONGUC -
PL/SQL procedure successfully completed.
Also you may want to read related asktom thread - "Char Vs Varchar" http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1542606219593
and http://tahitiviews.blogspot.com/2007/05/less-is-more-more-or-less.html
Best regards.

Varchar2

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