I'm building some application based on LaraAdmin crud generator. I need a field to be a BigInt since the possible values are bigger than a normal Integer. How should I achieve that in order to not make the system crash?
Because it is stored already as an integer, simply change the database type to biginteger and it'll be fine as they both store numerical values.
Related
We are working with a table in a 3rd party database that does not have a primary key but does have a unique index.
I have therefore been looking at using the ORA_HASH function to produce a de facto unique Id by passing in the values of the columns in the unique index.
Unfortunately, I can already see that we have a few collisions, which means that we can't derive a unique id using this method.
Is there an alternative to ORA_HASH that would provide a unique id for a unique input?
I suppose I could generate an Id using DBMS_CRYPTO.Hash but I'd ideally like to get a numeric value.
Edit
The added complication is that I then need to store these records in another (SQL Server) database and then compare the records from the original and the replica tables. So rank doesn't help me here since records can be added or deleted in the original table.
DBMS_CRYPTO.HASH could be used to generate a high-bit hash (high enough to give you a very low, but not zero, chance of collisions), but it returns 'RAW' not 'NUMBER'.
To guarantee no collisions ever, you need a one-to-one hash function. As far as I know, Oracle does not provide one.
A practical approach would be to create a new table to map unique keys to a newly generated primary key. E.g., unique value ("ABC",123, 888) maps to 838491 (where you generated 838491 using a sequence).
You'd have to update the mapping table periodically, to account for inserted rows, and that would be a pain, but it would let you generate your own PKs and keep track of them without a lot of complication.
Have you tried:
DBMS_UTILITY.GET_HASH_VALUE (
name VARCHAR2,
base NUMBER,
hash_size NUMBER)
RETURN NUMBER;
Let's say I'm saving users in a database and I want each user to have a unique random ID (this isn't actually the case, just a simpler example). When I INSERT the user, is there a way to insert a unique random ID?
I know I can easily just do an auto-increment column so that each row would have a unique integer, but I need a random number for this system specifically.
Sample of what my standard insert query for a new user:
INSERT INTO 'Users' VALUES ('RandomID', 'Bleh', 'Bleh2') (random value here, 1, 2)
I was wondering the same and found an interesting answer in this article: use a pre-populated table.
You create before hand a table of n rows with unique random numbers, using any method (for example, by trying to insert random numbers in a UNIQUE field and silently failing when the number isn't unique, until you get the number of rows needed).
Once that table is created you are 100% certain that the numbers in it are unique, and you can simply use them sequentially and discarding them after use (or not).
When using this method you need to have some kind of alert system for when you approach the limit of rows in the pre-populated table, so that you can generate a new set of values anew.
Sqlite has random() which returns a random integer. But it may not be unique every time. You can append time stamp or row_id with it to get unique random number.
Based on this documentation for the C API function sqlite3_randomness(), it might be possible to make a table's primary key random by creating a dummy row and forcing it's primary key value to the largest possible ROWID. Any new rows after that should be random.
That said, I don't know that that behavior is contractual or just a current implementation detail. Use at your own risk.
I'm working on a project in MVC 3 (first time using!). One question I keep running into is how to specify datatypes. For example, why have a field of type Nvarchar that has a length of 4000 when you only need a length of 10. As far as I can tell, there is no definitive compilation of specifying server data types for your database. I've been fairly successful so far (Below are some of the ones I've found), and please correct me if I am wrong. My main question is if there is a way to specify a Tinyint (1 byte) in MVC 3.
Here's some of the popular ones I've found:
Smallint: Specify field as Int16
Bigint: Specify field as Int64
Nvarchar(n): Add [StringLength(n)] above your variable in your Model
bit: Seems simple, but for first-time programmers - specify your field as a bool.
DateTime: There are so many flavors of DateTime, and to specify, initialize your field in your model as DateTime, and specify the type by placing [DataType(DataType.YourPreferredFormat)] above the variable, where "YourPreferredFormat" is a date/time related option of the enum DataType (DateTime, Date, Time, Duration). I'm not 100% clear on this though, so if anyone knows how each correlates, that would be great to know.
Per this answer to c-sharp-equivalent-of-sql-server-2005-datatypes it appears that you need to use Byte.
I have a little problem with Enterprise Architect by Sparx System.
Im trying to model database schema for Oracle. I created table with primary key with data type long. But when im trying to modify column properties (set AutoNum = true) I see empty properties. I read documentation of EA and saw that I need to setup this property to generate sequence syntax.
When I change data type to number, or switch database to mysql (for example) everything is alright, there are properties so Im able to modify AutoNum value.
Did you had similar problem and found solution ? or maybe im doing something wrong.
regards
It's becouse Oracle use sequence instead of autoincrement option. I've checked it and I think you have to use NUMBER column type and then set AutoNum property (you have to select Generate Sequences in options to get proper DDL code too). Instead of LONG data type you can set PRECISION and SCALE options on NUMBER type ie NUMBER(8) mean you can have 8 digits number and it can be set up to 38, so if you don't want to store info about every star in the universe will be enought for your scenario :)
I currently use INT as type for primary key in JavaDB (Apache Derby), but since I'm implementing an distributed system I would like to change the type to java.util.UUID. A few questions about this:
What datatype in JavaDB/Derby should I use for UUID? I have seen CHAR(16) FOR BIT DATA been mentioned but I don't know much about it. Is VARCHAR(16) an alternative?
How should I use it with JDBC? E.g. in an PreparedStatement, how should I set and get an UUID?
If I later would likte to change database to SQL Server, is there a compatible datatype to java.util.UUID?
Simply, How should I use UUID with JavaDB/Derby and JDBC?
UUID is a 128 bit value. The CHAR(16) FOR BIT DATA type reflects that it is bit data stored in character form for conciseness. I don't think VARCHAR(16) would work because it doesn't have the bit flag. The database would have to be able to convert the binary data to character data which deals with encoding and is risky. More importantly, it wouldn't buy you anything. Since a UUID is always 128 bits, you don't get the space savings from using VARCHAR over CHAR. So you might as well use the intended CHAR(16) FOR BIT DATA.
With JDBC, I think you use the get/setBytes() method since it is dealing with small amounts of binary data. (Not positive, would have to try this)
And no idea about the SQL Server part.
If you still want to use the UUID object in your code you can use fromString to create UUID objects from the DB and toString to store them in the DB.
You could convert the UUID to a string and store it as VARCHAR. Most UUID string formats are similar to this one: 32 digits separated by hyphens: 00000000-0000-0000-0000-000000000000, so then you'd want a VARCHAR(36), or make it something like VARCHAR(64) if you please, since it doesn't hurt to have extra 'space' available in your VARCHAR -- only the actual digits are stored.
Once you've converted it to a string, just call Statement.SetString to include it in your INSERT statement.