I have a table with CLOB column but I want to modify the CLOB of length >>
I executed this command "Alter table TableName (flddata CLOB length 100 Gb);
but i there is an error accorded "Invalid alter table option"
I want to increase the size of the field, how is that??
Thanks in advance
A clob column has no limit in the specification of the type. So, when you define a column as CLOB, it has no size associated the same as other string types ( char, varchar2 ).
However, the limit of what you can store there is defined by this:
CLOB Maximum size: (4 GB - 1) * DB_BLOCK_SIZE initialization parameter (8 TB to 128 TB)
Related
I created a table like this:
CREATE TABLE table(
id INTEGER GENERATED ALWAYS AS IDENTITY,
nome VARCHAR2(100 CHAR)
)
ALTER TABLE table ADD CONSTRAINT table_pk PRIMARY KEY (ID);
CREATE UNIQUE INDEX TABLE_UNIQ_IDX ON TABLE(NOME ASC);
ALTER TABLE table ADD (PERC NUMBER(1, 2) NOT NULL);
Then I tried to write 2 records on it:
INSERT INTO TABLE(NOME,PERC)VALUES('a',0.8);
INSERT INTO TABLE(NOME,PERC)VALUES('b',0.2);
Then I received this error:
ORA-01438: valor maior que a precisão especificada usado para esta coluna
Translated:
ORA-01438: value larger than specified precision allows for this column
I tried select cast (0.8 as number(1,1)) from dual; and it worked but when I tried select cast (0.8 as number(1,2)) from dual; I received the same error.
I then tried select cast (0.81 as number(1,2)) from dual; and received the same ORA-01438.
I changed my field to number(1,1), no big deal, but how does this "Number" data type work?
Shouldn't select cast (0.81 as number(1,2)) from dual; have worked?
Why does select cast (0.81 as number(2,2)) from dual; work and
select cast (0.81 as number(2,3)) from dual; does not?
Thanks for any help
If you have NUMBER(precision, scale) then precision is the number of digits and scale is the number of decimal places.
So, NUMBER(1, 2) has a single digit and 2 decimal places. The minimum value it can store is -0.09 and the maximum it can store is +0.09.
NUMBER(2,2) works as it stores 2 digits in 2 decimal places (from -0.99 to +0.99).
NUMBER(2,3) does not work as it stores 2 digits in 3 decimal places (from -0.099 to +0.099).
What you said, is that perc column should accept numeric values whose length is 1, and out of that 1, you want to keep 2 decimal places. That won't work.
SQL> create table test (perc number(1, 2));
Table created.
SQL> insert into test values (0.8);
insert into test values (0.8)
*
ERROR at line 1:
ORA-01438: value larger than specified precision allowed for this column
Perhaps you meant to put it vice versa?
SQL> alter table test modify perc number(2, 1);
Table altered.
SQL> insert into test values (0.8);
1 row created.
SQL>
I am trying to load a string of length more than 4000 into table of column type CLOB. I know we can do this using ananymous block. But how can I use this block in control file?
You need to provide the max size of the clob as following:
LOAD DATA
INFILE <your_filename>
INTO TABLE <your_table_name>
FIELDS TERMINATED BY '<your_separator>'
TRAILING NULLCOLS
(
id,
<your_clob_column> CHAR (6000), -- max value of your clob col, default is 255
other_fields
)
see the default is 255 so it will throw an error if you do not specify the size and load the data with length > 255 so It is better to always use size as mentioned above.
Cheers!!
I have a VARCHAR field that only allows 12 characters max. How do I change character allowance to 9 or 15 for example?
Google succeeds in telling me what the max number of characters in VARCHAR in any given version of Oracle database. I know, I get that. I just want to ALTER the column character allowance within that range.
alter table table_name MODIFY (column_to_change varchar(new size))
ALTER TABLE tbl_name MODIFY col_name column_definition;
So if you have:
CREATE TABLE table_name (
value VARCHAR2(12)
);
Then you can do:
ALTER TABLE table_name MODIFY value VARCHAR2(15 BYTE);
and the column will have a capacity of 15 bytes.
Or:
ALTER TABLE table_name MODIFY value VARCHAR2(9 CHAR);
and the column will have a capacity of 9 characters.
I have a field in a table that is varchar2, 4000 bytes. There are over 50000 rows. Not all rows have data in this field. Few data fields are over 255 bytes, but some are 4000. To place the table in a new application, I need to shorten the field to 255 bytes.
Is there a SQL statement that will reduce the length to 255? I realize data will be lost, that is part of the cost of the new application. The cut should be arbitrary, just stopping the data at 255 no matter the circumstance.
update b set text2 = substr(text2,1,255);
then alter table to set length of column to 255 :
alter table b MODIFY "TEXT2" varchar2(255 byte);
My goal is to execute a query (SELECT), fetch results and output them as text. Query is given as a parameter and can be e.g. select * from t.
I use OCIStmtPrepare and OCIStmtExecute, then I can describe columns of the query by OCIParamGet and series of OCIAttrGet. Suppose I get OCI_ATTR_DATA_TYPE = 12 (DATE) for one of the columns. Then OCI_ATTR_DATA_SIZE = 7 -- this is size of internal DATE representation.
I want to get this DATE as text, with respect to currect NLS settings. For that I use OCIDefineByPos with dty = SQLT_STR. It works alright, but I also need to supply a buffer for fetching. The question is: what size of buffer do I need?
Evidently it depends on NLS_DATE_FORMAT. I believe that Oracle knows this value:
SQL> create table x as select to_char(sysdate) d from dual;
Table created.
SQL> select value from nls_session_parameters where parameter='NLS_DATE_FORMAT';
VALUE
----------------------------------------
DD.MM.RR
SQL> select data_length from dba_tab_columns where table_name='X';
DATA_LENGTH
-----------
8
This is the exact length. Only when date format is masked from Oracle (by a function, for example), it uses absolute maximum (?) value of 75:
SQL> create or replace function get_date_format return varchar2 is
2 begin
3 return 'DD.MM.RR';
4 end;
5 /
Function created.
SQL> create table x as select to_char(sysdate,get_date_format) d from dual;
Table created.
SQL> select data_length from dba_tab_columns where table_name='X';
DATA_LENGTH
-----------
75
All said above applies to NUMBER as well.
So, is it possible to get length of text representation of a column in OCI?
The maximum buffer size for any date is 75. The maximum buffer size for any number is 42.
I hope that helps.
You can determine needed buffer size by calling OCIAttrGet for OCI_ATTR_DISP_SIZE attribute. It returns 40 for NUMBER, 75 for DATE, N for VARCHAR2(N). Add 1 byte for Null-termination and you good to go.
Yes - the trick is that in C, a string is really a pointer to a character array, so you would say char* mystring = OCIStringPtr(envhp, x); where x is a pointer to an OCIString, which you can get back by connecting with OCI_OBJECT set and asking for a SQLT_VST instead of an SQLT_STR. The actual memory for the string is allocated for you in the global env by OCI behind the scenes.