I have a table with a column in the format VARCHAR2(2000 CHAR). This column contained a row containing comma-separated numbers (ex: "3;3;780;1230;1;450.."). Now the situation has changed. Some rows contain data in the old format, but some contain the following data (ex: "BAAAABAAAAAgAAAAHAAAAAAAAAAAAAAAAQOUw6.."). Maybe it's blob or clob. How can I check exactly? And how can I read it now? Sorry for my noob question :)
The bad news is you really can't. Your column is a VARCHAR2 so it's all character data. It seems like what you're really asking is "How do I tell if this value is a comma separated string or a binary value encoded as a string?" So the best you can do is make an educated guess. There's not enough information here to give a very good answer, but you can try things like:
If the value is numeric characters with separators (you say commas but your example has semicolons) then treat it as such.
But what if the column value is "123", is that a single number or a short binary value?
If there are any letters in the value, you know it's not a separated list of numbers, then treat it as binary. But not all encoded binary values will have letters.
Try decoding it as binary, if it fails, maybe it's actually the separated list. This probably isn't a good one.
Related
I'd like to add a large string (above 76k characters) to CLOB column in Oracle database.
I need to run a script from liquibase framework.
How can achive this?
Simple insert
INSERT INTO table_clob (clob_column) VALUES (to_Clob('string above 72000 chars...'));
with and without to_clob() method is returning exception like:
ORA-01704: string literal too long
Cannot load data from file as described here with procedure: https://oracle-base.com/articles/8i/import-clob
as I don't have priviliges to any directory
Searched google but didn't enounter any solution for my requirement.
Any advice?
UPDATE:
After hours of searching finally found a workaround here: https://stackoverflow.com/a/49817056/1622703
It is not sufficient as I need to cut the text for 3 chunks manually (with around 30k chars), but it works.
Now just need to figure our how to do it dynamically in case that the string will have vary lenghts of chars (above 10k chars for example).
A hard-coded string enclosed in single quotes is known as a string literal. An example is 'Hello world'. Another example is the very long string you are trying to insert in the table. By contrast, 'abc' || 'def' is a string expression but it is not a string literal. Similarly, to_char(sysdate, 'yyyy-mm-dd') is a string expression, but not a literal. "Literal" means constant, hard-coded text.
The issue you are facing has nothing to do with insert, or to_clob(), or the data type of columns in your table, etc. It only has to do with the string literal itself.
In Oracle, a string literal can be at most 4000 bytes long (or 32767 bytes if the database is set up with extended MAX_STRING_SIZE). PERIOD! There is no way around it.
So, the question is, how can you ever get a string as long as the one you have into a table with a CLOB column. The answer depends on how you are receiving the string in the first place. The best option would be if it came in chunked already - as a collection of strings, with a tag (an id) to keep track of which fragment belongs to which CLOB and an ordinal number (to show if it's the first chunk, the second, etc.) Then you could re-assemble them using TO_CLOB() on the first chunk, plus the concatenation operator.
If your process is to type 72000 characters at the keyboard, you will have to type 4000 of them at a time, enclose in single quotes, and use the concatenation operator (essentially doing by hand what I described above). You would also have to use TO_CLOB() on the first fragment (otherwise the concatenation will fail).
Another option is for the string to come as a value, from some application that supports long strings (something compatible with Oracle's CLOB) and that can hand over such values to the Oracle database without the need to write out the hard-coded string in full.
So, the ball is in your court. The first question is, Where is the long string coming from in the first place?
I have a column where I want to write down numbers, but the numbers are long, 25 characters, and I could miss type it so at least knowing that I have typed the correct amount of characters would be helpful.
When typing in Google spreadsheets, I can validate the answer of a column within another column by using: '=IF(LEN(B1)=25,B1,"wrong number of digits")'
which means it would return the cell value if has 25 characters, but if its any other amount it will say wrong number, yet I need to use another column...
Is there any way that while I am typing in a cell it would let me proceed if right number of characters or give an error if I have wrong number of characters, in the same column?
UNTESTED
Please try a Data, Validation..., rule of:
=and(B1>999999999999999,len(B1)=25)
I'm writing a script which supposed to merge some data from sql-based db. Each row has a long-integer as a primary key (incremental). I was thinking about hashing these ids so that they'll somehow 'look' like the other ids already in my RethinkDB table. What I'm trying to achive here is to avoid dups in case of an attempt to merge the same data again, but keeping the original integers as ids along with the generated ids of the data saved directly to RethinkDB's table feels weird.
Can I do that?
How does RethinkDB generate auto ids anyways?
And am I approaching this correctly..?
RethinkDB uses a string-encoding of 128 bit UUIDs (basically hashed integers).
The string format looks like this: "HHHHHHHH-HHHH-HHHH-HHHH-HHHHHHHHHHHH" where every 'H' is a hexadecimal digit of the 128 bit integer. The characters 0-9 and a-f (lower case) are used.
If you want to generate such UUIDs from an existing integer, I recommend hashing the integer first. This will give you an even distribution over the whole key space (this makes sharding easier and avoids hotspots).
As a second step you have to format the hash value in a string of the format shown above. If you don't have enough digits, it's fine to leave some of the last 'H' as constant 0.
If you really want to go into the details of UUID generation, here are two links for further reading:
RFC 4122 "A Universally Unique IDentifier (UUID) URN Namespace" https://www.rfc-editor.org/rfc/rfc4122
RethinkDB's implementation of UUID generation and formatting https://github.com/rethinkdb/rethinkdb/blob/next/src/containers/uuid.cc
I'm new to Oracle, I'm using oracle 11g. I'm storing postal codes of UK. Values are like these.
N22 5HF
SW1 4JD
N14 8IT
N22 1JT
E1 5DP
e1 8DS
E3 8TU
I should be able to easily compare first four characters of each postal code.
What is the best data type to store these data ?
As a slight variation on Lalit's answer, since you want the outward code rather than a fixed substring of the first four characters (which could incude a space and the start of the inward code), you can create a virtual column based on the first word of the value:
postcode varchar2(8),
outward_code generated always as
(substr(postcode, 1, instr(postcode, ' ', 1, 1) - 1))
And optionally, but probably if you're using this to search, an index on the virtual column.
This assumes the post codes are formatted properly in the first place. It won't work if you don't always have the space between the outward and inward codes. And to answer your original question, the actual post code should be a varchar2(8) column to hold alphanumeric valus up to the maximum size and with the standard format.
SQL Fiddle demo.
I should be able to easily compare first four characters of each postal code.
Then keep these first four characters in a separate column. And index this column. You could keep the other characters in different column. Now, if the codes are a mixture of alphanumeric characters, then you are left with VARCHAR2 data type.
Your query predicate would like -
WHERE post_code_col = substr('N22 5HF', 1, 4)
Thus the indexed column post_code_col would be efficient in performance.
On 11g, you have the option to create a virtual column. However, indexing it would be equivalent to a function-based index. So I woukd prefer the first way as I suggested above.
It is better to normalize the table during the design phase, else the issues would start creeping in later.
In my opinion you should use varchar2 data type because this field will not going to be in mathematical calculations (they should not be int or decimal) and these fields are not big enough (so this should not be text)
How do you guys treat empty strings with Oracle?
Statement #1: Oracle treats empty string (e.g. '') as NULL in "varchar2" fields.
Statement #2: We have a model that defines abstract 'table structure', where for we have fields, that can't be NULL, but can be "empty". This model works with various DBMS; almost everywhere, all is just fine, but not with Oracle. You just can't insert empty string into a "not null" field.
Statement #3: non-empty default value is not allowed in our case.
So, would someone be so kind to tell me - how can we resolve it?
This is why I've never understood why Oracle is so popular. They don't actually follow the SQL standard, based on a silly decision they made many years ago.
The Oracle 9i SQL Reference states (this has been there for at least three major versions):
Oracle currently treats a character value with a length of zero as null. However, this may not continue to be true in future releases, and Oracle recommends that you do not treat empty strings the same as nulls.
But they don't say what you should do. The only ways I've ever found to get around this problem are either:
have a sentinel value that cannot occur in your real data to represent NULL (e.g, "deoxyribonucleic" for a surname field and hope that the movie stars don't start giving their kids weird surnames as well as weird first names :-).
have a separate field to indicate whether the first field is valid or not, basically what a real database does with NULLs.
Are we allowed to say "Don't support Oracle until it supports the standard SQL behaviour"? It seems the least pain-laden way in many respects.
If you can't force (use) a single blank, or maybe a Unicode Zero Width Non-Break Space (U+FEFF), then you probably have to go the whole hog and use something implausible such as 32 Z's to indicate that the data should be blank but isn't because the DBMS in use is Orrible.
Empty string and NULL in Oracle are the same thing. You want to allow empty strings but disallow NULLs.
You have put a NOT NULL constraint on your table, which is the same as a not-an-empty-string constraint. If you remove that constraint, what are you losing?