What is varchar2(80 char) ?

hi all
What is varchar2(80 char) ??
and what is difference between
varchar2(80 char) and varchar2(80)
Thank You.

Hi;
There are many good blog,site also oracle documents avaliable at internet. Please check below
http://www.google.com.tr/#hl=tr&q=data+type%2Boracle&oq=data+type%2Boracle&aq=f&aqi=&aql=&gs_sm=e&gs_upl=78610l83657l0l23l20l1l8l2l0l234l1701l2.5.4&fp=c759c1635a43d17d&biw=1259&bih=793
You can check also:
http://www.orafaq.com/wiki/VARCHAR2
http://www.orafaq.com/faq/what_is_the_difference_between_varchar_varchar2_and_char_data_types
Regard
Helios

Similar Messages

Difference between varchar2(4000 byte) & varchar2(4000 char

Hi,
My existing database NLS parameters as follows
CHARACTER SET US7ASCII
NATIONAL CHARACTER SET AL16UTF16
created a test database to support globalization, I changed as follows
CHARACTER SET UTF8
NATIONAL CHARACTER SET UTF8
some of the table column datatypes are varchar2(4000)
I would like to know what is difference between VARCHAR2(4000 BYTE) and VARCHAR2(4000 CHAR).
Thanks

Indeed, VARCHAR2(x BYTE) means that the column will hold as much characters as will fit into x bytes. Depending on the character set and particular characters this may be x or less characters.
For example, a VARCHAR2(20 BYTE) column in an AL32UTF8 database can hold 20 characters from the ASCII range, 10 Latin letters with umlaut, 10 Cyryllic, 10 Hebrew, or 10 Arabic letters (2 bytes per character), or 6 Chinese, Japanese, Korean, or Devanagari (Indic) characters. Or a mixture of these characters of any total length up to 20 bytes.
VARCHAR2(x CHAR) means that the column will hold x characters but not more than can fit into 4000 bytes. Internally, Oracle will set the byte length of the column (DBA_TAB_COLUMNS.DATA_LENGTH) to MIN(x * mchw, 4000), where mchw is the maximum byte width of a character in the database character set. This is 1 for US7ASCII or WE8MSWIN1252, 2 for JA16SJIS, 3 for UTF8, and 4 for AL32UTF8.
For example, a VARCHAR2(3000 CHAR) column in an AL32UTF8 database will be internally defined as having the width of 4000 bytes. It will hold up to 3000 characters from the ASCII range (the character limit), but only 1333 Chinese characters (the byte limit, 1333 * 3 bytes = 3999 bytes). A VARCHAR2(100 CHAR) column in an AL32UTF8 database will be internally defined as having the width of 400 bytes. It will hold up to any 100 Unicode characters.
The above implies that the CHAR limit works optimally if it is lower than 4000/mchw. With such restriction, the CHAR limit guarantees that the defined number of characters will fit into the column. Because the widest character in any Oracle character set has 4 bytes, if x <= 1000, VARCHAR2(x CHAR) is guaranteed to hold up to x characters in any database character set.
The declaration VARCHAR2(x):
- for objects defined in SYS schema means VARCHAR2(x BYTE),
- for objects defined in other schemas it means VARCHAR2(x BYTE) or VARCHAR2(x CHAR), depending on the value of the NLS_LENGTH_SEMANTICS parameter of the session using the declaration (see the NLS_SESSION_PARAMETERS view).
After an object is defined, its BYTE vs CHAR semantics is stored in the data dictionary and it does not depend on the NLS_LENGTH_SEMANTICS any longer. Even Export/Import will not change this.
Character length semantics rules are valid for table columns and for PL/SQL variables.
-- Sergiusz

Difference between VARCHAR2(40 BYTE) and VARCHAR2(40 CHAR)

What is the difference between using VARCHAR2(40), VARCHAR2(40 BYTE0, and VARCHAR2(40 CHAR)

With a single byte character set the two definitions are effictively equal, but with a multibyte character set the two definitions will be different. Say you have built Oracle using a fixed 2 byte character set. 40 characters would be 80 bytes so the varchar2(40 BYTES) would hold only 20 characters.
Search on NLS parameters and database character set for more information.
HTH -- Mark D Powell --

Problem creating cache group for a table with data type varchar2(1800 CHAR)

Hi,
I am using TimesTen 7.0 with Oracle 10.2.0.4 server. While creating Cache Group for one of my table I'm getting the following error.
5121: Non-standard type mapping for column TICKET.DESCRIPTION, cache operations are restricted
5168: Restricted cache groups are deprecated
5126: A system managed cache group cannot contain non-standard column type mapping
The command failed.
One of my filed type in oracle table is Varchar2(1800 CHAR). If I change the filed size to <=1000 it (E.g. Varchar2(1000 CHAR)) then the Create Cache command works fine.
MyDatabase Character Set is UTF8.
Is it possible to solve without changing the filed size in the Oracle Table?
Request your help on this.
Thanks,
Sunil

Hi Chris.
The TimesTen server and the Oracle Client is installed on a 32-bit system.
1. ttVersion
TimesTen Release 7.0.5.0.0 (32 bit Linux/x86) (timesten122:17000) 2008-04-04T00:09:04Z
Instance admin: root
Instance home directory: /appl/TimesTen/timesten122
Daemon home directory: /var/TimesTen/timesten122
Access control enabled.
2. Oracle DB details
SQL> select * from v$version;
BANNER
Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bi
PL/SQL Release 10.2.0.3.0 - Production
CORE 10.2.0.3.0 Production
TNS for Linux: Version 10.2.0.3.0 - Production
NLSRTL Version 10.2.0.3.0 - Production
Oracle Client - Oracle Client 10.2.0.4 running in a 32 bit Linux/x86
3. ODBC Details
Driver=/appl/TimesTen/timesten122/lib/libtten.so
DataStore=/var/TimesTen/data
PermSize=1700
TempSize=244
PassThrough=2
UID=testuser
OracleId=oraclenetservice
OraclePwd=testpwd
DatabaseCharacterSet=UTF8
Thanks,
Sunil

DIFFERENCE BETWEEN THE DATA DECLARATIONS NVARCHAR2 AND VARCHAR2(x CHAR)

CAN ANYONE HELP ME FIND THE DIFFERENCE BETWEEN THE DATA DECLARATIONS; NVARCHAR2 AND VARCHAR2(x CHAR), WHERE X IS THE SIZE OF DATA TO BE HELD WITH THE VARIABLE OR ATTRIBUTE

Duplicate posting....
Difference between nvarchar2(10) and varchar2(10 char )
Difference between nvarchar2( 10) and varchar2( 10 char)
Please refer also...
Nvarchar2

Difference between nvarchar2( 10) and varchar2( 10 char)

Hi ,
I had to enhance my application's DB to support unicode data entries(Multilingual data entries) and retrieval. I want to know the basic difference between the following data type decalrations:
nvarchar2( 10) and varchar2( 10 char)
Can any one suggest me which would be a optimum choice?
regards,
Siddarth

Yes, you are almost correct.
Can you read Japanese Character ? (There is no need to understand Japanese words meanings).
Are you ready? Let's go!
SQL> create table tab_size(col varchar(3));
Table created.
SQL> insert into tab_size values ('abc');
1 row created.
SQL> insert into tab_size values ('abcd');
insert into tab_size values ('abcd')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_size values('ｱｲｳ'); /* This is 3 characters (3byte) */
1 row created.
SQL> insert into tab_size values('ｱｲｳｴ'); /* This is 4 characters (4byte) */
insert into tab_size values('ｱｲｳｴ')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_size values ('あ'); /* This is 1 character (2bytes) */
1 row created.
SQL> insert into tab_size values ('あい'); /* This is 2 characters (4bytes) */
insert into tab_size values ('あい')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_size values ('aあ'); /* This is 2 characters (3bytes) */
1 row created.
SQL> insert into tab_size values ('abあ'); /* This is 3 characters (4bytes) */
insert into tab_size values ('abあ')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_SIZE"."COL" (actual: 4, maximum: 3)
SQL> drop table tab_size;
Table dropped.
SQL> create table tab_char (col varchar2(3 char));
Table created.
SQL> insert into tab_char values ('abc');
1 row created.
SQL> insert into tab_char values ('abcd');
insert into tab_char values ('abcd')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_CHAR"."COL" (actual: 4,
maximum: 3)
SQL> insert into tab_char values ('あいう'); /* This is 3 characters (6bytes) */
1 row created.
SQL> insert into tab_char values ('あいうえ'); /* This is 4 characters (8bytes) */
insert into tab_char values ('あいうえ')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_CHAR"."COL" (actual: 4, maximum: 3)
SQL> insert into tab_char values ('aあい'); /* This is 3 characters (5bytes) */
1 row created.
SQL> insert into tab_char values ('abあい'); /* This is 4 characters (6bytes) */
insert into tab_char values ('abあい')
ERROR at line 1:
ORA-12899: value too large for column "USHI"."TAB_CHAR"."COL" (actual: 4, maximum: 3)谢谢。
ありがとう。
Thank you for reading.

What is VARCHAR2?

My question is this.....
1. What is the difference between VARCHAR2? form VARCHAR & CHAR?
2. Does VARCHAR2 is supported in ADO? What MDAC version?
3. Effect of changing CHAR to VARCHAR2 in tables in sp's.
thanks

But if you have NULL in such a column then it will not occupy any space.Umm, up to a point Lord Copper...
SQL> desc VC
Name                                      Null?    Type
CHARCOL1                                           CHAR(10)
CHARCOL2                                           CHAR(10)
VARCHAR2COL1                                       VARCHAR2(10)
VARCHAR2COL2                                       VARCHAR2(10)
VARCHAR2COL3                                       VARCHAR2(10)
SQL> INSERT INTO vc VALUES ('1', null, '1', '1234567890', null)
2 /
1 row created.
SQL> exec dbms_stats.gather_table_stats(user, 'VC')
PL/SQL procedure successfully completed.
SQL> SELECT column_name
2          , avg_col_len
3          , char_length
4          , char_used
5 FROM user_tab_columns
6 WHERE   table_name = 'VC'
7 /
COLUMN_NAME                    AVG_COL_LEN CHAR_LENGTH C
CHARCOL1                                11          10 B
CHARCOL2                                 1          10 B
VARCHAR2COL1                             2          10 B
VARCHAR2COL2                            11          10 B
VARCHAR2COL3                             0          10 B
SQL> The CHAR column always has that one point overhead, even when it's null, unlike the VARCHAR2 column.
Cheers, APC

Primary Keys and VARCHAR2 vs CHAR datatypes???

Could someone please tell me if there is documentation concerning the performance implications of creating a Primary Key using a VARCHAR2 datatype vs a CHAR datatype?

Well with a CHAR datatype, a value of ‘abc’ equates to ‘abc ’.
So that if the value of ‘abc’ already existed in the PK in the table and someone tried to Insert another row with a value of ‘abc ‘, it would return a unique constraint violation (the rule from the user being that a value with or without trailing spaces is the same value).
But if the PK column is defined as VARCHAR2, both the 'abc' and the 'abc ' could be Inserted into the Table because in the nonpadded comparison they are not equal.
Would defining the column as a VARCHAR2 with a Check Constraint to RTRIM the column be a better way to go?

Converting RPAD output from VARCHAR2 to CHAR

I am trying to create a 1000-character fixed-width file using SQL*Plus. The query consists of 3 fields with a pad of 25 characters each, with the remaining 925 characters as filler using spaces. Using RPAD I can insert spaces between the three field values, but because the RPAD function uses VARCHAR2 to return the result it is not recognizing the ~945 filler spaces I need at the end of each row.
Is there a way to convert the output of RPAD to a CHAR data type in the query itself? Maybe something equivalent to the CONVERT function in t-SQL?
Query I'm using:
Select RPAD(Col1, 25, ' ') || RPAD(Col2, 25, ' ') || RPAD(Col3, 950, ' ') From Table1;
Thanks,
Matt

Hi,
Welcome to the forum!
You can ihave trailing spaces (950 of them if you want, no problem) in a VARCHAR2 column. I suspect your font-end tool is not displaying them.
The SQL*Plus commands
SET TRIM OFF
SET TRIMSPOOOL OFFshould guarantee that trailing spaces are displayed in screen- and SPOOL file output, respectively.
Also, make sure your lines are long enough:
SET LINESIZE 1000If you still have a problem, post a complete test script (including all the SQL*PLus formatting commands you use) as well as a query. (Something using dual or scottt.dept should illustrate the problem adequately).

What is the "continue" char in SQL?

If I'm writing a big like of code in SQL*Plus what is the char that I should use to break the line physically but not logically?
Thanks.
PB

Single hyphen.
(I would post an example but the forum software can't handle it...)
btw the SQL*Plus manual is here:
Contents
Index
"Continuing a long SQL*Plus command" is the fourth entry in the index, so I'm a little surprised you missed it when you looked.
Edited by: William Robertson on May 21, 2011 8:49 AM

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 & char comparison

which data type must be choosen for fixed length data.
varchar2 or char?
Is there any advantage of CHAR for fixed length data.
}s there any disadvatage of VARCHAR for fixed length data.
Thanks very much.
Fatih Sami
null

Depending on Oracle's internals there are some other considerations in choosing CHAR or VARCHAR as well as the order the columns should be defined when creating the table (especially for data warehouse tables).
Ram - would you comment on the following from Oracle's perspective?
1. How much space is taken by length bytes for variable length fields?
2. Is any space taken for length bytes for fixed length fields?
3. Does Oracle take advantage of knowing how many contiguous fixed length fields are at the start of each record?
If VARCHAR and VARCHAR2 require two length bytes (to store the length of the field) then
VARCHAR2(2) - requires 2 bytes if null or empty and 4 bytes if two bytes are data
CHAR(2) - requires 2 bytes in all cases
The following comments apply to the database from one of Oracle's competitor's but I though they apply to Oracle also - Ram?
1. Use fixed-length fields whenever possible. The DB engine is VERY efficient at finding and processing the contiguous fixed-length fields at the start of each row. One the first variable-length field is reached access to all remaining fields uses a leap-frog process. For example, assume that all 35 fields of a table are variable-length. To reach column 35 requires leaping over the first 34 columns. This is typically done by using a loop such as that described in the following pseudo-code:
POINT TO BEGINNING OF THE RECORD
SET THE COLUMN COUNT TO 1
SET DESIRED COLUMN COUNT TO 35
LOOP WHILE COLUMN COUNT <> DESIRED COLUMN COUNT
LOAD THE LENGTH BYTES
ADD THE LENGTH BYTES TO THE RECORD POINTER
INCREMENT THE COLUMN COUNT
END LOOP
---the column is found
RETRIEVE THE COLUMN VALUE
The problem is that column 35 can begin in a different place for every record. If you have ever looked at a CSV file in an editor and tried to find a particular column (such as status code) you can understand the problem. The above loop is exactly what people use with CSV files. If you want column 35 you find and count 34 commas.
Fixed-length columns at the start of the record ALWAYS begin at the same offset from the start of the record. If column 1 through 10 are each 4 bytes long then column 11 begins at byte 41 IN EVERY RECORD. The DB engine knows how many contiguous fixed-length fields are at the start of the record and how long each of them is (this is basic data dictionary information). Thus it can simply index directly to column 11 (or any of the others) without using a loop).
Base plus Index addressing is one of the fundamental address modes on most CPUs. Intel cpus allow two index registers to be used: you can not only index directly to the start of an array but (if elements are fixed length) can index directly to any given array element.
2. Put all the fixed-length columns up front and make the flag and heavily used columns (such as status code) fixed length.
3. Put all variable-length fields after the fixed_length fields (see #1 above)
4. Order the variable-length fields based on WHERE clause and ORDER BY usage highest usage first
The fewer fields the DB engine has to leap frog to get to the desired field the less time it takes. The WHERE clause controls which records get selected.
5. Order remaining variable-length fields based on how often they are selected in queries. These are the fields that are not used in the WHERE clause but retrieve data items. For example, if USER_ID is often retrieved but not used in the WHERE clause it would go after the #4 group of fields but at the start of the #5 group of fields.
6. Order remaining variable-length fields based on size: shortest first. There is less to leap frog.
7. Put large variable-length fields in a separate table. Large in this context usually means large in relation to the block size or buffer size used by the database to retrieve data. On NT the block size might be 2K. If the DB has to leap frog a 2000 byte COMMENT_TXT field (that isnt even needed for the current query) it might need to read another databas e block or chained record block.
Oracle will need to confirm which, if any, of the above items apply. My tests appear to indicate that they all do.
null

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
Copyright (c) 1982, 2005, Oracle. All rights reserved.
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.

How to find out if colums is defined as VARCHAR2 in bytes or char?

Hello,
I'd like to know if it is possible to find out if a colum table (or view) is defined as a VARCHAR2 in bytes or in CHAR on Oracle 10g.
When I do a desc, it shows only VARCHAR2 with its length but not if it is bytes or char. How can I know for sure?
Thanks,

SQL> create table t
id    varchar2 (10 char),
id2   varchar2 (10 byte)
Table created.
SQL> select column_name, data_type, char_used
from cols
where table_name = 'T'
COLUMN_NAME                                   DATA_TYPE       CHAR_USED
ID                                            VARCHAR2        C
ID2                                           VARCHAR2        B
2 rows selected.

IOT without overflow treats differently char/varchar2

Hi,
test case with 8k block size:
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
With the Partitioning, Automatic Storage Management and Data Mining options
SQL>
     create table test1 (x number primary key, y char(2000)) ORGANIZATION INDEX;
Table created.
SQL>
     create table test2 (x number primary key, y varchar2(2000)) ORGANIZATION INDEX;
create table test2 (x number primary key, y varchar2(2000)) ORGANIZATION INDEX
ERROR at line 1:
ORA-01429: Index-Organized Table: no data segment to store overflow row-pieces
SQL>
     create table test2 (x number primary key, y varchar2(1000)) ORGANIZATION INDEX;
create table test2 (x number primary key, y varchar2(1000)) ORGANIZATION INDEX
ERROR at line 1:
ORA-01429: Index-Organized Table: no data segment to store overflow row-pieces
SQL>
     create table test2 (x number primary key, y varchar2(500)) ORGANIZATION INDEX;
Table created.why does it fail with varchar2 but not with char?
Thanks,
Joaquin Gonzalez
Edited by: user4070490 on 10-feb-2011 23:41
Maybe it is something different with characterset used for char and varchar:
     select * from V$NLS_PARAMETERS;
PARAMETER               VALUE
NLS_LANGUAGE            AMERICAN
NLS_TERRITORY           SPAIN
NLS_CURRENCY            €
NLS_ISO_CURRENCY        SPAIN
NLS_NUMERIC_CHARACTERS ,.
NLS_CALENDAR            GREGORIAN
NLS_DATE_FORMAT         dd/mm/yyyy hh24:mi:ss
NLS_DATE_LANGUAGE       AMERICAN
NLS_CHARACTERSET        AL32UTF8
NLS_SORT                BINARY
NLS_TIME_FORMAT         HH24:MI:SSXFF
NLS_TIMESTAMP_FORMAT    DD/MM/YYYY HH24:MI:SS.FF3
NLS_TIME_TZ_FORMAT      HH24:MI:SSXFF TZR
NLS_TIMESTAMP_TZ_FORMAT DD/MM/RR HH24:MI:SSXFF TZR
NLS_DUAL_CURRENCY       €
NLS_NCHAR_CHARACTERSET AL16UTF16
NLS_COMP                BINARY
NLS_LENGTH_SEMANTICS    CHAR
NLS_NCHAR_CONV_EXCP     FALSEddl after creation is:
CREATE TABLE "EXPLOTACION"."TEST1"
(    "X" NUMBER,
       "Y" CHAR(2000 CHAR),
        PRIMARY KEY ("X") ENABLE
) ORGANIZATION INDEX NOCOMPRESS PCTFREE 10 INITRANS 2 MAXTRANS 255 NOLOGGING
TABLESPACE "EXPLOTACION"
PCTTHRESHOLD 50;
CREATE TABLE "EXPLOTACION"."TEST2"
(    "X" NUMBER,
       "Y" VARCHAR2(500 CHAR),
        PRIMARY KEY ("X") ENABLE
) ORGANIZATION INDEX NOCOMPRESS PCTFREE 10 INITRANS 2 MAXTRANS 255 NOLOGGING
TABLESPACE "EXPLOTACION"
PCTTHRESHOLD 50;

its about size of colunm not datatype
SQL>/
create table test4 (x number primary key, y char(4000)) ORGANIZATION INDEX;
ERROR at line 1:
ORA-00910: specified length too long for its datatype
Elapsed: 00:00:00.56
SQL>create table test4 (x number primary key, y char(400)) ORGANIZATION INDEX;
Table created.
Elapsed: 00:00:00.28
SQL>

What is varchar2(80 char) ?

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