I have a field in my table "marital status" , the user has to choose (radiobutton) if he's (married, divorced, single, voeuf)
What should I make the type of this field?
Is there a boolean type?
marital status doesn't sound like a boolean anyway. It sounds like an enumeration. A boolean would be married (Y/N), although I think in this day and age you might want to be able to store multiple kinds of relationships in there, and you specified yourself that you need to store 'devorced' as well, so a boolean is out of the question.
So I'd recommend making a table named MaritalStatus, having an ID and a description. Store the various states in there, and make a foreign key to MaritalStatusID in your table.
Make it an INT field , Create another table in your database something like
CREATE TABLE dbo.MaritalStatus
(
M_ID INT PRIMARY KEY NOT NULL,
M_Status NVARCHAR(20)
)
GO
INSERT INTO dbo.MaritalStatus
VALUES
(1, 'Single'),(2,'Married'),(3,'Divorced'),
(4,'Widowed'),(5,'Other'),(6,'Prefer Not to say').... bla bla
Now in your Table in "Marital Status" field refer to a user Marital Status using INT values from dbo.MaritalStatus table's "M_ID".
Boolean or in SQL bit datatype is best when you have a situation where something can be TRUE or NOT TRUE, for someone's Marital Status there can be more than two possible values therefore you should create a separate table for all the possible Marital Status and use Foreign key constraint.
The boolean equivalent for T-SQL is bit.
Though, it seems like you want more than a yes/no answer. In this case use an int and then convert the int to an enum.
Edit: Dukeling removed the C# tag in an edit, so I am not sure how relevant this part is anymore /Edit
The enum:
enum MaritalStatus
{
Single,
Married,
Divorced,
...
}
The int from DB:
int maritalStatusFromDB = //value from DB
Convert int to enum:
MaritalStatus maritalStatus = (MaritalStatus)maritalStatusFromDB;
Be aware that your database may contain int values that are not defined in your enum, such as 10. You can check whether maritalStatusFromDB is a valid MaritalStatus as follows:
bool isValid = Enum.IsDefined(typeof(MaritalStatus), maritalStatusFromDB);
if( isValid == false )
{
//handle appropriately
}
Related
For example, if I want to frequently update a user's score during a session,
is there a more performant way than - UPDATE score FROM [databaseName] WHERE name = [username]
I feel like I should not be continuously needing to search through the entire database when the value's location has been previously found.
Thanks in advance
You wouldn't search through the entire database if you had an index on name:
create index idx_<table>_name on <table>(name);
where <table> is the name of the table you are referring to, not the database.
Incidentally, if you wanted to update the table, you would use update, not select. But update can still use the index.
You can use properties here you can search and update only the database when you need it.
private int score;
public int Score
{
get
{
score = searchDatabase();
return score;
}
set
{
UpdateDatabase(value);
score = value;
}
}
Debug.Log(Score);
The only thing that comes to mind that resembles what you mention as the value's location, is the value of the primary key column of the row with the value that you search for.
So, if the primary key in the table is id and you only have the name of the person, you can query once to get the row's id:
SELECT id FROM tablename WHERE name = ?
and then use that id in all subsequent updates:
UPDATE tablename SET score = ? WHERE id = ?
This is the fastest way to do the updates.
I would like to know if there is a way in sql to allow a column to have any value it wants for its attributes, but only one of them can be X value.
More specifically for easier explanations let's say i have:
create table status( current_status varchar(100), id integer )
what constraint should i add so i can only have up to one value of current_status='ACCEPTED' ?
EDIT:REMOVED mysql TAG
Partial index in Postgresql
create unique index index_accepted on status (current_status)
where current_status = 'ACCEPTED'
I know that the question is very long and I understand if someone doesn't have the time to read it all, but I really wish there is a way to do this.
I am writing a program that will read the database schema from the database catalog tables and automatically build a basic application with the information extracted from the system catalogs.
Many tables in the database can be just a list of items of the form
CREATE TABLE tablename (id INTEGER PRIMARY KEY, description VARCHAR NOT NULL);
so when a table has a column that references the id of tablename I just resolve the descriptions by querying it from the tablename table, and I display a list in a combo box with the available options.
There are some tables however that cannot directly have a description column, because their description would be a combination of other columns, lets take as an example the most important of those tables in my first application
CREATE TABLE bankaccount (
bankid INTEGER NOT NULL REFERENCES bank,
officeid INTEGER NOT NULL REFERENCES bankoffice,
crc INTEGER NOT NULL,
number BIGINT NOT NULL
);
this as many would know, would be the full account number for a bank account, in my country it's composed as follows
[XXXX][XXXX][XX][XXXXXXXXXX]
^ ^ ^ ^
bank id | crc account number
|
|_ bank office id
so that's the reason of the way my bankaccount table is structured as is.
Now, I would like to have the complete bank account number in a description column so I can display it in the application without giving a special treatment to this situation, since there are some other tables with similar situation, something like
CREATE TABLE bankaccount (
bankid INTEGER NOT NULL REFERENCES bank,
officeid INTEGER NOT NULL REFERENCES bankoffice,
crc INTEGER NOT NULL,
number BIGINT NOT NULL,
description VARCHAR DEFAULT bankid || '-' || officeid || '-' || crc || '-' || number
);
Which of course doesn't work since the following error is raised1
ERROR: cannot use column references in default expression
If there is any different approach that someone can suggest, please feel free to suggest it as an answer.
1 This is the error message given by PostgreSQL.
What you want is to create a view on your table. I'm more familiar with MySQL and SQLite, so excuse the differences. But basically, if you have table 'AccountInfo' you can have a view 'AccountInfoView' which is sort of like a 'stored query' but can be used like a table. You would create it with something like
CREATE VIEW AccountInfoView AS
SELECT *, CONCATENATE(bankid,officeid,crc,number) AS FullAccountNumber
FROM AccountInfo
Another approach is to have an actual FullAccountNumber column in your original table, and create a trigger that sets it any time an insert or update is performed on your table. This is usually less efficient though, as it duplicates storage and takes the performance hit when data are written instead of retrieved. Sometimes that approach can make sense, though.
What actually works, and I believe it's a very elegant solution is to use a function like this one
CREATE FUNCTION description(bankaccount) RETURNS VARCHAR AS $$
SELECT
CONCAT(bankid, '-', officeid, '-', crc, '-', number)
FROM
bankaccount this
WHERE
$1.bankid = this.bankid AND
$1.officeid = this.officeid AND
$1.crc = this.crc AND
$1.number = this.number
$$ LANGUAGE SQL STABLE;
which would then be used like this
SELECT bankaccount.description FROM bankaccount;
and hence, my goal is achieved.
Note: this solution works with PostgreSQL only AFAIK.
I am having two tables One is a Master table called TRANSACTION and second is record of the transaction this table is called TRANSACTION_RECORD.
TRANSACTION
CREATE TABLE `e3_transaction` (
`transactionid` bigint(20),
`transactiontype` varchar(10),
`transactionstatus` varchar(10),
PRIMARY KEY (`transactionid`)
);
TRANSACTION_RECORD
CREATE TABLE `e3_as2805msg4` (
`transectionid` bigint(20),
`messageType` int(4),
`cardAcceptorName` varchar(40),
`adNational` varchar(1000),
`adPrivate` varchar(1000),
KEY `transectionidFK` (`transectionid`),
CONSTRAINT `transectionidFK` FOREIGN KEY (`transectionid`) REFERENCES `e3_transaction` (`transactionid`)
);
It will have one to one mapping between Transaction and transaction record. It means one transaction can have only one record. I have kept this table separately for some reasons. So my class will look like this:
#Entity
#Table(name = "e3_transaction")
public class Transaction {
#Id
#GeneratedValue(generator = "assigned-by-code")
#GenericGenerator(name = "assigned-by-code", strategy = "assigned")
#Column(name = "transactionid", unique = true, nullable = false)
private Long transactionid;
#Column(name = "transactiontype", nullable = false, length = 10)
private String transactiontype;
#Column(name = "transactionstatus", nullable = false, length = 10)
private String transactionstatus;
#oneToOne
private TransactionRecord record;
}
I want to persist both objects at a same time. when I persist a TRANSACTION, TRANSACTION_RECORD should be persist in it's table. Is there any way to do this ?
You can change the table structure if you want. Only thing i need it TWO tables.
Works with
#OneToOne(cascade=CascadeType.ALL)
#MapsId
private TransactionRecord record;
TransactionRecord must have an #Id of the same type as Transaction with no value generation.
Tried with Hibernate as JPA 2.0-provider.
There are a few options to map this, but it looks like you are handling it with two separate entities. As both entities share the same primary key value, your reference mapping will need to change based on which entity you wish to have controlling the pk value generation - as it stands, the e3_transaction.transactionid field is being set by two separate mappings; the transactionid long and the TransactionRecord record reference.
If you wish to use the #MapsId as is suggested in the other answer, you will need to move your #GeneratedValue code to the TransactionRecord entity, as the JPA provider will use the value in the referenced TransactionRecord to set the transactionid attribute and the database field. This is a simple elegant solution, but you can also remove the Long transactionid attribute from Transaction and just mark the record reference with #Id (instead of #MapsId). The long transactionId value within TransactionRecord would still be used as Transaction's id for EntityManager getReference and find calls.
A different option that allows keeping the #GeneratedValue on the transactionid within Transaction is to define the #JoinColumn annotation on the record reference and specify that the field is insertable=false, updatable=false. You then need to modify the TransactionRecord so that it has a back relationship to the Transaction so that it can pull the transectionid value from the Transaction instance to use as its id. This can be accomplished by simply marking the relationship with #ID though.
Is it possible to create a table which has a check constraint on one of the column whose value lies within the result set given by another sql query
eg.
create table tablename
(
name varchar(10),
rollno int
)check rollno in (select rollno from anotherDatabase.TableName,candidateRoll)
or any thing like that.
I dont have to use it anywhere but still want to know.
If you can't achieve what you want with a foreign key reference, so you can if you wrap the SELECT statement in a function call.
Your check constraint expression may look something like:
(dbo.SomeFunction([col1]) != 0)
The function might look like this (assuming the column is a varchar):
create function dbo.SomeFunction(#arg varchar(max))
returns bit
as
begin
return
(
select count(*) from SomeOthertable where col2 = #arg
)
end
EDIT (2010/06/9): Regarding Anthony's comment, my testing has shown that a count(*) value of greater than 1 is still returned as 1. So it would seem that the function is okay, even though it should probably explicitly return 1 or 0. Or, if you are interested in the actual rowcount, change the return type from BIT to INT.
Yes: foreign key for same database links
create table tablename
(
name varchar(10),
rollno int FOREIGN KEY (candidateRoll) REFERENCES OtherTableName (candidateRoll)
)
If it's a different database then use code e.g. insert via stored proc or enforce via a trigger