I am using oracle 10gr2. I am trying to enforce a constraint on a column called "score" such that only fractions can be entered.
More specifically, a the format should contain one digit in the numerator and one digit in the denominator, such that a user can only enter a fraction such as 3/4,2/5,or 7/8. The column only accepts numbers as the input. Can anyone show me the SQL to use?
If I understand correctly, I think the proper way to do this is to store the data in two columns. This especially makes sense if the top number is a user's actual score on a problem and the bottom number is the possible score, which is what it sounds like you are doing. This will enable you to sum up scores using the built in number functions in Oracle rather than parsing strings. Then, you limit the size of each column to (0-9) by using the type NUMBER(1,0). For example:
alter table table_name add (
column possible number(1,0),
column actual number(1,0)
);
If you have data in the score column already, you then copy your values over from there to your new columns. Finally, you drop that column.
alter table table_name drop score;
Also, I'd do a search on "Oracle less than constraint", because you probably don't want the actual score to exceed the possible, and probably do a similar constraint to make the possible score greater than zero.
I don't have an instance of Oracle to test against, but here are some pointers and some untested code:
Pointers:
Look here on how to create a check constraint: http://www.techonthenet.com/oracle/check.php
After you know that, you can use Regex to validate the input. Read here for further reference: http://psoug.org/reference/regexp.html
You are probably going to use REGEX_LIKE and it would look like something like this:
ALTER TABLE your_table
add CONSTRAINT check_your_field
CHECK (REGEXP_LIKE(your_field, '^[0-9]+/[0-9]+$'));
Warning: this is not guaranteed to be fully functional code. It's a lead. Read, research and adjust accordingly.
A caveat: 1/0 will be considered valid by the Regex above, but we all know it should not be. There's a way you can know about the second part of the fraction. Read the Regex link, everything you need to know is there.
The domain of valid values is finite and small. Therefore, consider putting them all in a table, using a fixed width text column (i.e. three characters) and a create a foreign reference to this lookup table, rather than a CHECK constraint.
Related
I currently have a column in a DB2 table which is being passed through web calls and procedure by a character-encrypted value. It is type CHARACTER(13) with a CSSID for encryption.
This has become a huge pain to accommodate through multiple APIs but was initially intended to allow us a unique ID to use in calls that wasn't the primary key.
In DB2-400, what would be the next best thing as far as a 13 or more character string that is unique and randomly created upon insert, but doesn't require decryption (just a plain string)?
Is there a commonly-gravitated-to method for this? We aren't passing secure data, so there's no need for encryption, but we just want a randomly created and unique character
Try hex(generate_unique()). It's unique CHAR(26) string.
Or to_char(timestamp(generate_unique()), 'YYYYMMDDHH24MISSFF6'). You may play with format of the to_char function as well. May be useful to use, let's say, reverse format like FF6SSMIHH24DDMMYYYY to avoid unique index page contention upon heavy insert activity.
This is a comment that doesn't fit in the comments section.
I don't have access to a DB2-400 (anymore), but I tested the code below in DB2 10.5 for Linux.
create sequence seq1;
select concat('A', varchar_format(next value for seq1, '000000000000')) as my_id
from sysibm.sysdummy1;
Result, if you run it 4 times in a row:
A0000000000001
A0000000000002
A0000000000003
A0000000000004
Maybe there's something equivalent in DB2-400.
Sounds like you might be using GENERATE_UNIQUE()
GENERATE_UNIQUE function returns a bit data character string 13 bytes
long (CHAR(13) FOR BIT DATA)
Doesn't really have anything to do with encryption...
And pretty much the ideal solution in my opinion generating a unique value other than a simple numeric identity. So what the problem you are having?
I want to create a database containing multiple tables using postgres 11 and i'm currently creating a table which contain brackets in the heading of the column (as shown as follows).
Table - supp_details
supp_id|supp_name | supp_weight(Kg)|
Can i add units to the heading and what is the proper way to do so with sql?
I'm a fresher to query writing, so please help me with this.
You could place the column name in quotes, e.g. use "supp_weight(Kg)", but it is best to avoid placing special characters or keywords as object names. Instead, I suggest using the following name:
supp_weight_kg
It is just a single string requiring no escaping, and makes it clear what the units are. A better option might be to just use supp_weight, and maybe just keep a note somewhere that the column uses kilograms as the unit by default.
You will need to use quoted identifiers but I strongly recommend not to do that:
create table supp_details
(
supp_id integer,
supp_name text,
"supp_weight(kg)" integer
);
Adding bracket symbols into your column names is possible but probably a bad idea. If you want to micromanage the name just for display purposes of the end result, you should probably do it in an alias, using the AS keyword.
SELECT supp_id, supp_name, supp_weight AS "supp_weight(Kg)" FROM ...
Or add the decorations on the client side before it displays the results.
I have a column of type bigint (ProductSerial) in my table. I need to filter the table by the Product serial using like operator. But I found that, like operator can't be used for integer type.
Is there any other method for this (I don't want to use the = operator).
If you must use LIKE, you can cast your number to char/varchar, and perform the LIKE on the result. This is quite inefficient, but since LIKE has a high potential of killing indexes anyway, it may work in your scenario:
... AND CAST(phone AS VARCHAR(9)) LIKE '%0203'
If you are looking to use LIKE to match the beginning or the end of the number, you could use integer division and modulus operators to extract the digits. For example, if you want all nine-digit numbers starting in 407, search for
phone / 1000000 = 407
Although I'm a bit late to the party, I'd like to add the method I'm using to match the first N given numbers (in the example, 123) in any numeric-type column:
SELECT * FROM MyTable WHERE MyColumn / POWER(10, LEN(MyColumn) - LEN(123)) = 123
The technique is similar to #dasblinkenlight's one, but it works regardless of the number of digits of the target column values. This is a viable workaround if your column contain numbers with different length and you don't want to use the CAST+LIKE method (or a calculated column).
For additional details on that (and other LIKE workarounds) check out this blog post that I wrote on this topic.
If you have control over the database you could add a calculated column to copy the integer value to a string:
ALTER TABLE MyTable
ADD CalcCol AS (CAST(ProductSerial AS VARCHAR)) PERSISTED
And query like:
SELECT *
FROM MyTable
WHERE ProductSerial LIKE '%2548%'
This will move the calculation to the insert/update and only on rows inserted/updated rather then converting every row for each query.
This may be a problem if there are a lot of updated to columns as it will add a very small overhead to these.
There may be a way to do it mathematically using modulus but this would take a lot of working out and testing.
You can change your Field PhoneNumbers and store as String and then use the Like You can alter your table so that you can use the LIKE statement, if you still want to use BIGint for your phone numbers, you cannot get the exact Phone Number without using = the method you can use is Between method that looks for the Numbers that are inside the range.
For the edited question: I think you should use = sign for their ID, or convert the Int to String and then Use Like.
The original question related to a phone number. OP has since edited it to refer to serial numbers. This answer refers to the original question only.
My suggestion is to avoid storing your phone numbers as integers in the first place, and thus the problem does not occur. My phone number is in the form, internationally, of:
+44 7844 51515
Storing it as an integer makes no sense here, as you will never need to do any mathematical operation on it, and you would lose the leading plus. Within the UK, it is:
07844 51515
and thus storing it as an integer would lose its leading zero. Unless you have a very very specific requirement to store it as an integer, you would fare significantly better storing it as a string instead.
[Note: Not actually my phone number]
I have a three tables
Results:
TestID
TestCode
Value
Tests:
TestID
TestType
SysCodeID
SystemCodes
SysCodeID
ParentSysCodeID
Description
The question I have is for when the user is entering data into the results table.
The formatting code when the row gets the focus changes the value field to a dropdown combobox if the testCode is of type SystemList. The drop down has a list of all the system codes that have a parentsyscodeID of the test.SysCodeID. When the user chooses a value in the list it translates into a number which goes into the value field.
The datatype of the Results.Value field is integer. I made it an integer instead of a string because when reporting it is easier to do calculations and sorting if it is a number. There are issues if you are putting integer/decimal value into a string field. As well, when the system was being designed they only wanted numbers in there.
The users now want to put strings into the value field as well as numbers/values from a list and I'm wondering what the best way of doing that would be.
Would it be bad practice to convert the field over to a string and then store both strings and integers in the same field? There are different issues related to this one but i'm not sure if any are a really big deal.
Should I add another column into the table of string datatype and if the test is a string type then put the data the user enters into the different field.
Another option would be to create a 1-1 relationship to another table and if the user types in a string into the value field it adds it into the new table with a key of a number.
Anyone have any interesting ideas?
What about treating Results.Value as if it were a numeric ValueCode that becomes an foreign key referencing another table that contains a ValueCode and a string that matches it.
CREATE TABLE ValueCodes
(
Value INTEGER NOT NULL PRIMARY KEY,
Meaning VARCHAR(32) NOT NULL UNIQUE
);
CREATE TABLE Results
(
TestID ...,
TestCode ...,
Value INTEGER NOT NULL FOREIGN KEY REFERENCES ValueCodes
);
You continue storing integers as now, but they are references to a limited set of values in the ValueCodes table. Most of the existing values appear as an integer such as 100 with a string representing the same value "100". New codes can be added as needed.
Are you saying that they want to do free-form text entry? If that's the case, they will ruin the ability to do meaningful reporting on the field, because I can guarantee that they will not consistently enter the strings.
If they are going to be entering one of several preset strings (for example, grades of A, B, C, etc.) then make a lookup table for those strings which maps to numeric values for sorting, evaluating, averaging, etc.
If they really want to be able to start entering in free-form text and you can't dissuade them from it, add another column along the lines of other_entry. Have a predefined value that means "other" to put in your value column. That way, when you're doing reporting you can either roll up all of those random "other" values or you can simply ignore them. Make sure that you add the "other" into your SystemCodes table so that you can keep a foreign key between that and the Results table. If you don't already have one, then you should definitely consider adding one.
Good luck!
The users now want to put strings into
the value field as well as
numbers/values from a list and I'm
wondering what the best way of doing
that would be.
It sounds like the users want to add new 'testCodes'. If that is the case why not just add them to your existing testcode table and keep your existing format.
Would it be bad practice to convert
the field over to a string and then
store both strings and integers in
the same field? There are different
issues related to this one but i'm not
sure if any are a really big deal.
No it's not a big deal. Often PO numbers or Invoice numbers have numbers or a combination of letters and numbers. You are right however about the performance of the database on a number field as opposed to a string, but if you index the string field you end up with the database doing it's scans on numeric indexes anyway.
The problems you may have had with your decimals as strings probably have to do with the floating point data types in which the server essentially estimates the value of the field and only retains accuracy to a certain number of digits. This can lead to a whole host of rounding errors if you are concerned about the digits. You can avoid that issue by using currency fields or the like that have static accuracy of the decimals. lol I learned this the hard way.
Tom H. did a great job addressing everything else.
I think the easiest way to do it would be to convert Results.Value to a "string" (char, varchar, whatever). Yes, this ruins the ability to do numeric sorting (and you won't be able to do a cast or convert on the column any longer since text will be intermingled with integer values), but I think any other method would be too complex to maintain properly. (For example, in the 1-1 case you mentioned, is that integer value the actual value or a foreign key to the string table? Now we need another column to determine that.)
I would create the extra column for string values. It's not true normalization but it's the easiest to implement and to work with.
Using the same field for both numbers and strings would work to as long as you don't plan on doing anything with the numbers like summing or sorting.
The extra table approach while good from a normalization standpoint is probably overly complex.
I'd convert the value field to string and add a column indicating what the datatype should be treated as for post processing and reporting.
Sql Server at least has an IsNumeric function you can use:
ORDER BY IsNumeric(Results.Value) DESC,
CASE WHEN IsNumeric(Results.Value) = 1 THEN Len(Results.Value) ELSE 99 END,
Results.Value
One of two solutions comes to mind. It kind of depends on what you're doing with the numbers. If they just represent a choice of some kind, then pick one. If you need to do math on it (sorting, conversion, etc..) then pick another.
Change the column to be a varchar, and then either put numbers or text in it. Sorting numerically will suck, but hey, it's one column.
Have both a varchar column for the text, and an int column for the number. Use a view to hide the differences, and to control the sorting if necessary. You can coalesce the two columns together if you don't care about whether you're looking at numbers or text.
I have a column containing the strings 'Operator (1)' and so on until 'Operator (600)' so far.
I want to get them numerically ordered and I've come up with
select colname from table order by
cast(replace(replace(colname,'Operator (',''),')','') as int)
which is very very ugly.
Better suggestions?
It's that, InStr()/SubString(), changing Operator(1) to Operator(001), storing the n in Operator(n) separately, or creating a computed column that hides the ugly string manipulation. What you have seems fine.
If you really have to leave the data in the format you have - and adding a numeric sort order column is the better solution - then consider wrapping the text manipulation up in a user defined function.
select colname from table order by dbo.udfSortOperator(colname)
It's less ugly and gives you some abstraction. There's an additional overhead of the function call but on a table containing low thousands of rows in a not-too-heavily hit database server it's not a major concern. Make notes in the function to optomise later as required.
My answer would be to change the problem. I would add an operatorNumber field to the table if that is possible. Change the update/insert routines to extract the number and store it. That way the string conversion hit is only once per record.
The ordering logic would require the string conversion every time the query is run.
Well, first define the meaning of that column. Is operator a name so you can justify using chars? Or is it a number?
If the field is a name then you will use chars, and then you would want to determine the fixed length. Pad all operator names with zeros on the left. Define naming rules for operators (I.E. No leters. Or the codes you would use in a series like "A001")
An index will sort the physical data in the server. And a properly define text naming will sort them on a query. You would want both.
If the operator is a number, then you got the data type for that column wrong and needs to be changed.
Indexed computed column
If you find yourself ordering on or otherwise querying operator column often, consider creating a computed column for its numeric value and adding an index for it. This will give you a computed/persistent column (which sounds like oxymoron, but isn't).