What Is the Major Difference Between Varchar2 and Char

What is the major difference between Varchar2 and char

Simple example to show the difference:

SELECT 
    '"'||CAST('abc' AS VARCHAR2(10))||'"', 
    '"'||CAST('abc' AS CHAR(10))||'"' 
FROM dual;


'"'||CAST('ABC'ASVARCHAR2(10))||'"' '"'||CAST('ABC'ASCHAR(10))||'"'
----------------------------------- -------------------------------
"abc"                               "abc       "                   
1 row selected.

The CHAR is usefull for expressions where the length of charaters is always fix, e.g. postal code for US states, for example CA, NY, FL, TX

What's the difference between VARCHAR and CHAR?

VARCHAR is variable-length.

CHAR is fixed length.

If your content is a fixed size, you'll get better performance with CHAR.

See the MySQL page on CHAR and VARCHAR Types for a detailed explanation (be sure to also read the comments).

What is the difference between varchar and varchar2 in Oracle?

As for now, they are synonyms.

VARCHAR is reserved by Oracle to support distinction between NULL and empty string in future, as ANSI standard prescribes.

VARCHAR2 does not distinguish between a NULL and empty string, and never will.

If you rely on empty string and NULL being the same thing, you should use VARCHAR2.

Difference between varchar2(10), varchar2(10 byte) and varchar2(10 char)

VARCHAR2(10 byte) will support up to 10 bytes of data, which could be as few as two characters in a multi-byte character sets.

VARCHAR2(10 char) could support as much as 40 bytes of information and will support to up 10 characters of data.

Varchar2(10) uses the current value of NLS_LENGTH_SEMANTICS to determine the limit for the string.

incase of byte, then it's 10 bytes.

incase of char, then it's 10 characters.

In multibyte character sets these can be different! So if NLS_LENGTH_SEMANTICS = byte, you may only be able to store 5 characters in your varchar2.
So varchar2(10 char) is explicit. This can store up to 10 characters. Varchar2(10) is implicit. It may store 10 bytes or 10 characters, depending on the DB configuration.

ocacle ask link

Oracle SQL difference between varchar2(n) and varchar2(n char)

Based on this resource

Oracle9i and above allow Varchar2 columns to be defined as a number of bytes VARCHAR2(50 BYTE) or a number of characters VARCHAR2(50 CHAR), the latter is useful if the database is ever converted to run a double-byte character set (such as Japanese), you won't have to edit the column sizes. The default measure, normally BYTE, is set with nls_length_semantics.

If you create a column as Varchar2 (50) but only store 10 bytes, then Oracle will only save 10 bytes to disc. This does not mean that you should just create Varchar2 (4000) columns 'just in case the space is needed', that is a really bad idea which will reduce the performance and maintainability of your application.

Difference between VARCHAR2(10 CHAR) and NVARCHAR2(10)

The NVARCHAR2 datatype was introduced by Oracle for databases that want to use Unicode for some columns while keeping another character set for the rest of the database (which uses VARCHAR2). The NVARCHAR2 is a Unicode-only datatype.

One reason you may want to use NVARCHAR2 might be that your DB uses a non-Unicode character set and you still want to be able to store Unicode data for some columns without changing the primary character set. Another reason might be that you want to use two Unicode character set (AL32UTF8 for data that comes mostly from western Europe, AL16UTF16 for data that comes mostly from Asia for example) because different character sets won't store the same data equally efficiently.

Both columns in your example (Unicode VARCHAR2(10 CHAR) and NVARCHAR2(10)) would be able to store the same data, however the byte storage will be different. Some strings may be stored more efficiently in one or the other.

Note also that some features won't work with NVARCHAR2, see this SO question:

• Oracle Text will not work with NVARCHAR2. What else might be unavailable?

When to use Char over Varchar2

Already asked and answered

Oracle datatype: Should I use VARCHAR2 or CHAR

Just to avoid confusion about much wrong information. Here are some information about difference including performance

Reference: https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:2668391900346844476

Since a char is nothing more than a VARCHAR2 that is blank padded out
to the maximum length - that is, the difference between the columns X
and Y below:

create table t ( x varchar2(30), y char(30) ); insert into t (x,y)
values ( rpad('a',' ',30), 'a' );

IS ABSOLUTELY NOTHING, and given that the difference between columns X
and Y below:

insert into t (x,y) values ('a','a')

is that X consumes 3 bytes (null indicator, leading byte length, 1
byte for 'a') and Y consumes 32 bytes (null indicator, leading byte
length, 30 bytes for 'a ' )

Umm, varchar2 is going to be somewhat "at an advantage performance
wise". It helps us NOT AT ALL that char(30) is always 30 bytes - to
us, it is simply a varchar2 that is blank padded out to the maximum
length. It helps us in processing - ZERO, zilch, zippo.

Anytime you see anyone say "it is up to 50% faster", and that is it -
no example, no science, no facts, no story to back it up - just laugh
out loud at them and keep on moving along.

There are other "made up things" on that page as well, for example:

"Searching is faster in CHAR as all the strings are stored at a
specified position from the each other, the system doesnot have to
search for the end of string. Whereas in VARCHAR the system has to
first find the end of string and then go for searching."

FALSE: a char is just a varchar2 blank padded - we do not store
strings "at a specified position from each other". We do search for
the end of the string - we use a leading byte length to figure things
out.

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