问题
We have a table in Oracle 11g with a varchar2 column. We use a proprietary programming language where this column is defined as string. Maximum we can store 2000 characters (4000 bytes) in this column. Now the requirement is such that the column needs to store more than 2000 characters (in fact unlimited characters). The DBAs don't like BLOB or LONG datatypes for maintenance reasons.
The solution that I can think of is to remove this column from the original table and have a separate table for this column and then store each character in a row, in order to get unlimited characters. This tble will be joined with the original table for queries.
Is there any better solution to this problem?
UPDATE: The proprietary programming language allows to define variables of type string and blob, there is no option of CLOB. I understand the responses given, but I cannot take on the DBAs. I understand that deviating from BLOB or LONG will be developers' nightmare, but still cannot help it.
UPDATE 2: If maximum I need is 8000 characters, can I just add 3 more columns so that I will have 4 columns with 2000 char each to get 8000 chars. So when the first column is full, values would be spilled over to the next column and so on. Will this design have any bad side effects? Please suggest.
回答1:
If a blob is what you need convince your dba it's what you need. Those data types are there for a reason and any roll your own implementation will be worse than the built in type.
Also you might want to look at the CLOB type as it will meet your needs quite well.
回答2:
You could follow the way Oracle stored their stored procedures in the information schema. Define a table called text columns:
CREATE TABLE MY_TEXT (
IDENTIFIER INT,
LINE INT,
TEXT VARCHAR2 (4000),
PRIMARY KEY (INDENTIFIER, LINE));
The identifier column is the foreign key to the original table. The Line is a simple integer (not a sequence) to keep the text fields in order. This allows keeping larger chunks of data
Yes this is not as efficient as a blob, clob, or LONG (I would avoid LONG fields if at all possible). Yes, this requires more mainenance, buf if your DBAs are dead set against managing CLOB fields in the database, this is option two.
EDIT:
My_Table below is where you currently have the VARCHAR column you are looking to expand. I would keep it in the table for the short text fields.
CREATE TABLE MY_TABLE (
INDENTIFER INT,
OTHER_FIELD VARCHAR2(10),
REQUIRED_TEXT VARCHAR(4000),
PRIMERY KEY (IDENTFIER));
Then write the query to pull the data join the two tables, ordering by LINE in the MY_TEXT field. Your application will need to split the string into 2000 character chunks and insert them in line order.
I would do this in a PL/SQL procedure. Both insert and select. PL/SQL VARCHAR strings can be up to 32K characters. Which may or may not be large enough for your needs.
But like every other person answering this question, I would strongly suggest making a case to the DBA to make the column a CLOB. From the program perspective this will be a BLOB and therefore simple to manage.
回答3:
You said no BLOB or LONG... but what about CLOB? 4GB character data.
回答4:
BLOB is the best solution. Anything else will be less convenient and a bigger maintenance annoyance.
回答5:
Is BFILE a viable alternative datatype for your DBAs?
回答6:
I don't get it. A CLOB is the appropriate database datatype. If your weird programming language will deal with strings of 8000 (or whatever) characters, what stops it writing those to a CLOB.
More specifically, what error do you get (from Oracle or your programming language) when you try to insert an 8000 character string into a column defined as a CLOB.
来源：https://stackoverflow.com/questions/2976154/how-to-store-unlimited-characters-in-oracle-11g