I want to implement a patients data base for our software, and have an issue with the foreign key statement. I am using the latest SQLite DLLs, with C#.
When I try to run below code:
dbConnection = "Data Source=SQLiteMyDatabase.db;foreign keys=true;";
if (connections == 0)
{
cnn = new SQLiteConnection(dbConnection);
cnn.Open();
this.ExecuteNonQuery("CREATE TABLE IF NOT EXISTS patients ( id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, name VARCHAR(100) NOT NULL;");
this.ExecuteNonQuery("CREATE TABLE IF NOT EXISTS images ( FOREIGN KEY (patientID) REFERENCES patients(id), nameRed VARCHAR(20) NOT NULL PRIMARY KEY;");
}
I get the error:
SQLite error near "FOREIGN": syntax error
Why does this happen?
In order to create a foreign key, you must first create the column:
CREATE TABLE IF NOT EXISTS images (
nameRed VARCHAR(20) NOT NULL PRIMARY KEY,
patientID INT,
FOREIGN KEY (patientID) REFERENCES patients(id)
);
Please note:
I moved the primary key column (nameRed) first in the list of columns created, but that's just convention. It could go second.
You use the data type VARCHAR and SQlite will accept that, but be aware that it gets mapped to type TEXT, the maximum length will be ignored, and you will be able to store other data types in the column. SQLite is a bit funny when it comes to data types (it has a very well thought-out system but it's quite different from most other SQL databases).
To make things more confusing, you are allowed to declare the PRIMARY KEY as a property of the column (although you can also do it after the list of columns as with the FOREIGN KEY).
Related
I use the MS Sync Framework to sync my SQL Server instance with a local SQL CE file to make it possible working offline with my Windows app.
I use GUIDs as keys. On my table I have a unique index on 2 columns: user_id and setting_id:
usersettings table
------------------
id PK -> I also tried it without this column. Same result
user_id FK
setting_id FK
value
Now I do the following:
I create a new record in this table in both databases - SQL Server and SQL CE with the same user_id and setting_id.
This should work and merge the data together since this can happen in real life. But I get an error when syncing saying the unique key constraint led to an error. The key pair already exists in the table.
A duplicate value cannot be inserted into a unique index. [ Table name = user_settings,Constraint name = unique_userid_settingid ]
Why can't MS sync handle that? It should not try to insert the key pair again. It should update the value if needed.
The issue is if you add the same key pair to different copies of the table, they get different IDs (GUIDs) as primary keys in this usersettings table.
As this is simply a many-to-many table between Users and Settings, there is no need to have that ID as a PK (or even a column at all).
Instead, just use a concatenated key of the two FKs e.g.,
CREATE TABLE [dbo].[usersettings](
[user_id] [UNIQUEIDENTIFIER] NOT NULL,
[setting_id] [UNIQUEIDENTIFIER] NOT NULL,
[value] [varchar](50) NOT NULL,
CONSTRAINT [PK_usersettings] PRIMARY KEY CLUSTERED ([user_id] ASC, [setting_id] ASC) );
Of course, include appropriate field settings (e.g., if you use VARCHARs to store the IDs) and relevant FKs.
As the rows inserted should now be identical on the two copies, it should merge fine.
If you must have a single column as a unique identifier for the table, you could make it meaningful e.g.,
the PK (ID) becomes a varchar (72)
it gets filled with CONCAT(user_ID, setting_id)
As the User_ID and Setting_ID are FKs, you should already have them generated so concatenating them should be easy enough.
Do you get the error during sync, then it should appear as a conflict, that you must solve in code.
https://learn.microsoft.com/en-us/previous-versions/sql/synchronization/sync-framework-2.0/bb734542(v=sql.105)
I also see this in the manual: By default, the following objects are not copied to the client database: FOREIGN KEY constraints, UNIQUE constraints, DEFAULT constraints, and the SQL Server ROWGUIDCOL property. This indicates poor support for your scenario
I suggest you remove the unique constraint from the device table.
This question already has answers here:
Duplicate entry for key 'PRIMARY' .Ignoring the spaces for strings
(2 answers)
Closed 5 years ago.
I have the following structure, mapped with Entity Framework 6 using the Database First principle:
Here is the source database:
CREATE TABLE `Foo` (
`Guid` VARCHAR(36),
`Name` VARCHAR(500) NOT NULL,
`Author` VARCHAR(100) NOT NULL,
PRIMARY KEY (`Guid`),
UNIQUE KEY `unique_fooname` (`Name`,`Author`));
CREATE TABLE `FooVersion` (
`Guid` VARCHAR(36),
`Version` INT,
`RefFooGuid` VARCHAR(36) NOT NULL,
PRIMARY KEY (`Guid`),
UNIQUE KEY `unique_fooversion` (`Version`,`RefFooGuid`),
CONSTRAINT `fk_foo_version`
FOREIGN KEY (`RefFooGuid`)
REFERENCES `Foo` (`Guid`)
ON DELETE NO ACTION
ON UPDATE NO ACTION);
CREATE TABLE `FooVersionPart` (
`Name` VARCHAR(250) NOT NULL,
`RefFooVersionGuid` VARCHAR(36) NOT NULL,
PRIMARY KEY (`Name`, `RefFooVersionGuid`),
INDEX `fk_fooversion_fooversionpart_idx` (`RefFooVersionGuid` ASC),
CONSTRAINT `fk_fooversion_fooversionpart`
FOREIGN KEY (`RefFooVersionGuid`)
REFERENCES `FooVersion` (`Guid`)
ON DELETE NO ACTION
ON UPDATE NO ACTION);
At one point in my code, I am creating a new foo like this:
var dbContext = new DbContext();
var newVersion = new FooVersion();
newVersion.Guid = Guid.NewGuid().ToString()
newVersion.Parts = sourceParts.Select(s => new FooVersionPart
{
Name = s.Name,
RefFooVersionGuid = newVersion.Guid
}.ToList();
var foo = new Foo
{
Author = "Me"
Guid = Guid.NewGuid().ToString(),
Name = "Foo"
};
dbContext.Foos.Add(foo);
foo.Versions.Add(newVersion);
dbContext.SaveChanges();
I am getting the following error during the SaveChanges:
Duplicate entry 'dim.proran.db.tmp.dataCallistHDay -9e6620f4-227d-44de-b781-5fd67' for key 'PRIMARY'
The errors occurs more specifically when EF is trying to insert one of the FooVersionPart (dim.proran.db.tmp.dataCallistHDay is the Name of that part and 9e6620f4-227d-44de-b781-5fd67 is the -truncated- RefFooVersionGuid of that part).
I have the absolute certainty sourceParts have no duplicate and neither in the database.
Here is the generated SQL:
INSERT INTO Foo [..];
INSERT INTO FooVersion [..];
INSERT INTO FooVersionPart [..];
INSERT INTO FooVersionPart [..];
INSERT INTO FooVersionPart [..];
INSERT INTO FooVersionPart [..];
Etc
The exception always occurs on the same FooVersionPart (dim.proran.db.tmp.dataCallistHDay). It is the 1910th elements of 2435. So EF is not trying to insert twice all parts, just one at the middle.
The weirdest thing is that it worked a while ago, and it does not work anymore with no changes in all the related stuff (no changes in the schema, no library update, no changes in the code). It works well in one of my environment, and it does not work with the same code in my dev environment.
One last thing, it is not specific to that Guid. At each attempt, the Guid is different (not the other inputs, so it still fails on dim.proran.db.tmp.dataCallistHDay), and at each attempt I get the same error.
Do you have any idea of what could cause that?
The exception message (Duplicate entry 'dim.proran.db.tmp.dataCallistHDay -9e6620f4-227d-44de-b781-5fd67' for key 'PRIMARY') combined with the primary key for the table it refers to (PRIMARY KEY ('Name', 'RefFooVersionGuid')) tells us that you are attempting to insert duplicate data into the table, specifically multiple FooVersionParts with the same name.
Now you say you have done a duplicate check on your source data, but what you may not know is that many (all?) SQL database don't count trailing spaces as part of the record. For example this query will actually return a record:
SELECT 1
WHERE 'abc' = 'abc '
So, as you confirmed, your data does have duplicate(s) that won't be spotted by a C# GroupBy but will be caught by the database engine. An easy solution is to trim the data before you group it, a good habit to get into, particularly with data inputted manually.
I get this error when i am trying to create a relational database:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' REFERENCES classes(Name))' at line 1
I used a Update method to update the data base and create new tables, the first Update method works but then the second one breaks it. This is my code
one.Update("CREATE TABLE classes (Name VARCHAR (30) , Primitive1 VARCHAR(30), Primitive2 VARCHAR(30), Primitive3 VARCHAR(30), PRIMARY KEY(Name)) ");
one.Update("CREATE TABLE primitives (Name VARCHAR(30), Size_bytes INT, Description TEXT, FOREIGN KEY (Classes), REFERENCES classes(Name))" );
You may have other problems, but you have an extra comma in the foreign key statement:
FOREIGN KEY (Classes), REFERENCES classes(Name)
should be:
FOREIGN KEY (Classes) REFERENCES classes(Name)
I note that you have no actual column called Classes in the table. Either you need to declare that, or you might mean:
FOREIGN KEY (Name) REFERENCES classes(Name)
EDIT:
And I'm a strong advocate of auto incrementing keys:
CREATE TABLE classes (
ClassesId int auto_increment primary key,
Name VARCHAR(30) not null unique,
Primitive1 VARCHAR(30),
Primitive2 VARCHAR(30),
Primitive3 VARCHAR(30)
);
CREATE TABLE primitives(
PrimitivesId int auto_increment primary key,
Name VARCHAR(30),
Size_bytes INT,
Description TEXT,
ClassId int references classes(ClassId)
);
Note the use of inline references. I'm sure some will disagree, but I find it easier to follow column definitions when they are in one place. Also, this adds auto-incrementing primary keys and uses the same column name for the primary key and foreign key.
Finally, having three columns that look the same -- Primitive1, Primitive2, and Primitive3 -- is usually a poor design. It is better to have another table with one row per class and "Primitive".
one.Update("CREATE TABLE primitives (Name VARCHAR(30), Size_bytes INT, Description TEXT, FOREIGN KEY (Classes) REFERENCES classes(Name))" );
is correct. You had comma , before REFERENCES
I have the following table:
create table tbl
(
id int identity(1,1),
val varchar(100)
)
Now when i use Entity Framework to map objects to this table, it works, however when i change the table definition as follows:
create table tbl1
(
id int,
val varchar(100)
)
Entity Framework does not maps objects to this table. Any clue as to why is this happening would be appreciated.
Entity Framework requires a Primary Key to generate a model from the database. If there is no Primary Key on a table it will simply select the non-nullable columns as a concatenated primary key and the Entity will be read/only.
In your first table identity definition makes your id column non-nullable so you were able to create an Entity. You should have seen this message while adding that table:
"The table/view 'tbl1' does not have a primary key defined. The key
has been inferred and the definition was created as a read-only
table/view."
In your second table however there is no non-nullable column and EF cannot create an Entity for it. See the message when you try to add it:
"The table/view 'tbl1' does not have a primary key defined and no
valid primary key could be inferred. This table/view has been
excluded. To use the entity, you will need to review your schema, add
the correct keys, and uncomment it."
Entity frameworks generally need a way to distinguish between two records in a table and so require a ID/Key discriminator which need not be a primary key constraint or a unique key constraint or an identity at the DB layer. But this discriminator, a column or a set of columns, should help the entity framework identify a record uniquely and distinguish it from other records. So, you need to define such a discriminator in your entity class at the C# layer.
I'm using SubSonic 3.0.0.3 and I can't seem to get the ActiveRecord .tt files to recognize and generate code for the foreign keys and relationships in my SQLite database.
I think it generates everything else just fine, but after looking at other snippets online it looks like there should be more generated code than just single classes in ActiveRecord.cs and Structs.cs for each of my tables. Looking inside Structs.cs, IsForeignKey is always false for every column, even the ones I have a foreign key defined for. Additionally, each Foreign Keys region is empty within each generated ActiveRecord class.
I'm using VS2008 with references to SubSonic 3.0.0.3, System.Data.SQLite 1.0.66.0, and System.Data.SQLite.Linq 2.0.38.0 in my project. I created the database using SQLite Expert Personal 3.1.0.2076. I made some dummy tables to try to test out how SubSonic handles one:many and many:many relationships. Here's the DDL SQLite Expert spits out for my small database:
CREATE TABLE [Person] (
[PersonID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
[PersonName] TEXT NOT NULL,
[PersonAge] INT NOT NULL
);
CREATE TABLE [Group] (
[GroupID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
[GroupName] TEXT NOT NULL,
[GroupDescription] TEXT NOT NULL
);
CREATE TABLE [Dog] (
[DogID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
[PersonID] INT NOT NULL CONSTRAINT [DogPersonFK] REFERENCES [Person]([PersonID]) ON DELETE CASCADE ON UPDATE CASCADE,
[DogName] TEXT NOT NULL);
CREATE TABLE [GroupPersons] (
[GroupID] INTEGER NOT NULL CONSTRAINT [GroupPersonToGroupFK] REFERENCES [Group]([GroupID]) ON DELETE CASCADE ON UPDATE CASCADE,
[PersonID] INTEGER NOT NULL CONSTRAINT [GroupPersonToPersonFK] REFERENCES [Person]([PersonID]) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT [sqlite_autoindex_GroupPersons_1] PRIMARY KEY ([GroupID], [PersonID]));
I know foreign keys are enabled and work in the database - SQLite Expert says they're on and when I change data in one place, like Person's PersonID, it does indeed change that PersonID in the Dog and GroupPersons tables. I've tried re-adding the database to the project, 'running custom tool' to get the .tt files to execute again, and even deleting them and adding them back. I can get a simple project to build that perform simple querying and insertions, however I tried just now to change the primary key of a single Person, Dog, or Group and x.Save() but System.Data.SQLite threw an exception for all three, saying SQLite error near "WHERE":syntax error. at the Save().
Any suggestions for what I should try to do next?
It seems that the FKTables attribute for each table is not assigned in the file "SQLite.ttinclude". So i add some lines of code and managed to generate foreign key code :
After line 16 (var schema = conn.GetSchema("COLUMNS");), insert :
var schemaForeignKeys = conn.GetSchema("FOREIGNKEYS");
After line 29 (tbl.Name = row["TABLE_NAME"].ToString();), insert :
tbl.FKTables = new List<FKTable>();
var foreignKeyTables = schemaForeignKeys.Select("TABLE_NAME='" + tbl.Name + "'");
foreach (var foreignKeyTable in foreignKeyTables) {
FKTable foreignKey = new FKTable();
foreignKey.ThisTable = foreignKeyTable["TABLE_NAME"].ToString();
foreignKey.ThisColumn = foreignKeyTable["FKEY_FROM_COLUMN"].ToString();
foreignKey.OtherTable = foreignKeyTable["FKEY_TO_TABLE"].ToString();
foreignKey.OtherColumn = foreignKeyTable["FKEY_TO_COLUMN"].ToString();
foreignKey.OtherClass = CleanUp(foreignKey.OtherTable);
foreignKey.OtherQueryable = foreignKey.OtherClass;
tbl.FKTables.Add(foreignKey);
}
And after line 53 (col.IsNullable=row["IS_NULLABLE"].ToString()=="True";), insert :
col.IsForeignKey = tbl.FKTables.Any(x => x.ThisColumn == col.Name);
This is for generate the foreign key code.
Moreover, you have maybe encounter a problem when you have to delete a record which has a column to be a foreign key in an other table ? For exemple :
Person(Id, Name)
Dog(Id, #PersonId)
If you have set the #PersonId foreign key on-delete action to "SET TO NULL", this won't work because foreign key support is disabled by default in SQLite 3.6.23.1 (version used by Data.SQLite 1.0.66.0).
To enable foreign key support, you have to execute this command with each connection :
PRAGMA foreign_keys = ON;
Now, this is not supported by Data.SQLite, but it will (in version 1.0.67.0, http://sqlite-dotnet2.cvs.sourceforge.net/viewvc/sqlite-dotnet2/SQLite.NET/System.Data.SQLite/SQLiteConnection.cs?r1=1.80&r2=1.81).
So you have to wait for the release or you can (like me) download the Data.SQLite source and compile the last version. It work great for me.
Good luck.
And sorry for my english :)
I'm trying to reason this. There seems to be two issues at hand:
Subsonic not recognising your foreign keys
The x.Save() function sending that error message.
SQLite will be enforcing referential integrity on its own, so while Subsonic does not see the foreign references, SQLite does, and that's why your updates go through. Subsonic does not drive SQLite, it is driving itself, which is fine.
I'm attempting to learn what SubSonic is and does. In the mean time, I have this hypothesis: the table definitions are not parsed correctly. If x.Save() is uses automatically generated SQL, it could be that the two issues are really just one.
To validate (or invalidate) this hypothesis, could you try defining the tables thus, giving the foreign keys as table attributes, not attributes of specific fields:
CREATE TABLE [Dog] (
[DogID] INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
[PersonID] INTEGER NOT NULL,
[DogName] TEXT NOT NULL,
FOREIGN KEY ([PersonID]) REFERENCES [Person]([PersonID]) ON DELETE CASCADE ON UPDATE CASCADE);
CREATE TABLE [GroupPersons] (
[GroupID] INTEGER NOT NULL,
[PersonID] INTEGER NOT NULL,
FOREIGN KEY ([GroupID]) REFERENCES [Group]([GroupID]) ON DELETE CASCADE ON UPDATE CASCADE,
FOREIGN KEY ([PersonID]) REFERENCES [Person]([PersonID]) ON DELETE CASCADE ON UPDATE CASCADE,
PRIMARY KEY ([GroupID], [PersonID]));