I need to find a field length for a text field in application. i.e, How many words or characters I can store in that field. Should I need to check it in DB or in code?
Firstly , Oracle prefer Varchar2 data type instead of varchar.
secondly, before Oracle 12C, the max length of varchar2 is 4000 in SQL , but in PL/SQL, the max length varchar2 is 32K; since 12C, it is same for SQL and PL/SQL, the max length of varchar2 is 32K.
Related
I use Oracle 12c. I have below table in my DB.
CREATE TABLE TEST_T (COL VARCHAR2(4000 CHAR));
I need insert multibyte characters in this table. The character is 3 byte character.
I am able to insert only 1333 (upto 3999 bytes) characters in table.
My expectation is to insert upto 1500 multibyte characters but I get ORA - 01461.
I don't want to change data type to CLOB or LONG.
Is there any way to use VARCHAR2(4000 CHAR) to achieve this.
Below is the code,
SET SERVEROUTPUT ON
DECLARE
LV_VAR CHAR(1):='プ'; -- 3 byte character
LV_STR VARCHAR2(32000) := '';
BEGIN
FOR I IN 1..1500
LOOP
LV_STR := LV_STR||LV_VAR;
END LOOP;
--
INSERT INTO TEST_T VALUES (LV_STR);
END;
/
Error report -
ORA-01461: can bind a LONG value only for insert into a LONG column
ORA-06512: at line 11
01461. 00000 - "can bind a LONG value only for insert into a LONG column"
*Cause:
*Action:
The problem is that the 4000 byte limit is a hard limit, regardless of whether the datatype is defined as VARCHAR2(4000 CHAR), VARCHAR2(4000 BYTE), or NVARCHAR2(4000). This means that multibyte characters will always have the chance of overflowing a max-size non-CLOB text column.
Oracle's table of Datatype Limits shows each of the VARCHAR2 variants as holding a max of 4000 bytes. And this is precisely the problem you have encountered.
You do have the option of increasing the max size for VARCHAR2 in your Oracle 12c database to 32k.
Here's how to do it: MAX_STRING_SIZE documentation
This is not something to be done without careful consideration: once you change your database to use extended VARCHAR2 strings you cannot go back.
Nevertheless, if your database is all your own and you like the idea of having 32K strings, then this feature was created specifically to address your situation.
Be careful to read the details of pluggable databases, container databases as they require different upgrade techniques. This is a change that cuts across the entire database so you want to get it right.
Use NVARCHAR2 instead of VARCHAR2
NCHAR and NVARCHAR2 are Unicode datatypes that store Unicode character data. The character set of NCHAR and NVARCHAR2 datatypes can only be either AL16UTF16 or UTF8 and is specified at database creation time as the national character set. AL16UTF16 and UTF8 are both Unicode encoding.
The maximum length of an NVARCHAR2 column is 4000 bytes. It can hold up to 4000 characters. The actual data is subject to the maximum byte limit of 4000. The two size constraints must be satisfied simultaneously at run time.
The maximum size for VARCHAR2 is 4000 bytes (VARCHAR2 max size) and is not 4000+ bytes for multibyte characters. You have to change the type to CLOB or NVARCHAR2.
The maximum byte length of an NVARCHAR2 depends on the configured national character set (NVARCHAR2).
I am very new to oracle and today I found about the data type VARCHAR2, and I wanted to learn more about it and google the datatype where I met the problem.
I have gone through few articles about the datatype, and I found out some direct opposite descriptions for VARCHAR2.
DESCRIPTION 1:
When you create a table with a VARCHAR2 column, you specify a maximum
column length (in bytes, not characters) between 1 and 2000 for the
VARCHAR2 column(article)
DESCRIPTION 2:
you can store up to 4000 characters in a VARCHAR2 column. (article)
As you can see it is bit confusing. Is VARCHAR2 is to specify the maximum column length or maximum characters length? Somebody please explain me which one is the correct one?
It depends on your Oracle version, but both articles are mostly incorrect.
When you DECLARE the column, you can either declare the stated length EXPLICITLY as either bytes or characters, or IMPLICITLY using your session's default.
Also, the maximum length is 4000 bytes, NOT characters. Even if you declare VARCHAR2(4000 CHAR), the column cannot store more than 4000 BYTES. It will store 4000 characters if they are all single-byte, otherwise it will store fewer than 4000 characters.
DESCRIPTION 2:
you can store up to 4000 characters in a VARCHAR2 column.
This is correct
The VARCHAR2 datatype stores variable-length character strings. When you create a table with a VARCHAR2 column, you specify a maximum string length (in bytes or characters) between 1 and 4000 bytes for the VARCHAR2 column.
=> varchar2 datatype is same as varchar datatype.
=> its datatype with variable lengh.
Ex. "name varchar2(20)" and pass the value of name is "Ram" so, LENGTH(name) is 3 NOT 20.
=> its internal datatype managed by oracle server only.
=> even if, you declare varchar oracle implicitely converts to into varchar2
I have a stored procedure in Oracle Database 10g where my input is a varchar2 but I'm having issues getting it to run when the input string is long (not sure of exact length maybe > 8000).
My thought is the 'intext varchar2' (as below) is by default is too small. In other cases where I need a longer string I might define a varchar2 as "intext2 VARCHAR2(32767);" I tried to define the size similarly in the code below but my syntax is incorrect.
create or replace PROCEDURE TESTPROC ( intext IN VARCHAR2
) AS ....
What is the (default) size of the intext varchar2?
Can that size be defined (increased)?
thanks
You cannot specify a size for a VARCHAR2 parameter to a procedure.
The procedure should happily accept strings up to 32k in size (the maximum size of a VARCHAR2 in PL/SQL). If it were a function that was being called from SQL rather than PL/SQL, the limit would be 4k because the maximum size of a VARCHAR2 in SQL is only 4k.
I have created an Oracle table with an indexed varchar2 column, called 'ID'.
A software I'm using is reading this table, but instead of running queries like
select * from table_name where ID='something'
it does (notice the extra "N" before the value)
select * from table_name where ID=N'something'
which is causing some kind of character conversion.
The problem is that, while the 1st query is performing a range scan, the 2nd is performing a full table scan.
Since I cannot modify the queries that this software is running, which data type should I use, instead of varchar2, so that the conversion performed by the 'N' function does not imply a full table scan?
The prefix N before the string is used to specify a NVARCHAR2 or NCHAR datatype.
When comparing NVARCHAR2s to VARCHAR2s, Oracle converts the VARCHAR2 variable to NVARCHAR2. This is why you are experiencing a FULL SCAN.
Use a NVARCHAR2 column instead of a VARCHAR2 in your table if you can't modify the query.
What is the difference between varchar and varchar2?
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.
Currently VARCHAR behaves exactly the same as VARCHAR2. However, the type VARCHAR should not be used as it is reserved for future usage.
Taken from: Difference Between CHAR, VARCHAR, VARCHAR2
Taken from the latest stable Oracle production version 12.2:
Data Types
The major difference is that VARCHAR2 is an internal data type and VARCHAR is an external data type. So we need to understand the difference between an internal and external data type...
Inside a database, values are stored in columns in tables. Internally, Oracle represents data in particular formats known as internal data types.
In general, OCI (Oracle Call Interface) applications do not work with internal data type representations of data, but with host language data types that are predefined by the language in which they are written. When data is transferred between an OCI client application and a database table, the OCI libraries convert the data between internal data types and external data types.
External types provide a convenience for the programmer by making it possible to work with host language types instead of proprietary data formats. OCI can perform a wide range of data type conversions when transferring data between an Oracle database and an OCI application. There are more OCI external data types than Oracle internal data types.
The VARCHAR2 data type is a variable-length string of characters with a maximum length of 4000 bytes. If the init.ora parameter max_string_size is default, the maximum length of a VARCHAR2 can be 4000 bytes. If the init.ora parameter max_string_size = extended, the maximum length of a VARCHAR2 can be 32767 bytes
The VARCHAR data type stores character strings of varying length. The first 2 bytes contain the length of the character string, and the remaining bytes contain the string. The specified length of the string in a bind or a define call must include the two length bytes, so the largest VARCHAR string that can be received or sent is 65533 bytes long, not 65535.
A quick test in a 12.2 database suggests that as an internal data type, Oracle still treats a VARCHAR as a pseudotype for VARCHAR2. It is NOT a SYNONYM which is an actual object type in Oracle.
SQL> select substr(banner,1,80) from v$version where rownum=1;
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
SQL> create table test (my_char varchar(20));
Table created.
SQL> desc test
Name Null? Type
MY_CHAR VARCHAR2(20)
There are also some implications of VARCHAR for ProC/C++ Precompiler options. For programmers who are interested, the link is at: Pro*C/C++ Programmer's Guide
After some experimentation (see below), I can confirm that as of September 2017, nothing has changed with regards to the functionality described in the accepted answer:-
Rextester demo for Oracle 11g:
Empty strings are inserted as NULLs for both VARCHAR
and VARCHAR2.
LiveSQL demo for Oracle 12c: Same results.
The historical reason for these two keywords is explained well in an answer to a different question.
VARCHAR can store up to 2000 bytes of characters while VARCHAR2 can store up to 4000 bytes of characters.
If we declare datatype as VARCHAR then it will occupy space for NULL values. In the case of VARCHAR2 datatype, it will not occupy any space for NULL values. e.g.,
name varchar(10)
will reserve 6 bytes of memory even if the name is 'Ravi__', whereas
name varchar2(10)
will reserve space according to the length of the input string. e.g., 4 bytes of memory for 'Ravi__'.
Here, _ represents NULL.
NOTE: varchar will reserve space for null values and varchar2 will not reserve any space for null values.
Currently, they are the same. but previously
Somewhere on the net, I read that,
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.
Also,
Emp_name varchar(10) - if you enter value less than 10 digits then remaining space cannot be deleted. it used total of 10 spaces.
Emp_name varchar2(10) - if you enter value less than 10 digits then remaining space is automatically deleted