Using fuelphp, is there a way to modify an existing \ORM\Model to convert it to \ORM\Model_Temporal? I started looking into creating a migration, which needs to 1) add the necessary columns to my table (not difficult); 2) update the primary key to include the new columns as part of a compound primary key (difficult). The problem I am having is that I don't see a method in the DBUtil that performs this operation.
What is the right way to do this?
Currently DBUtil does not include a way to alter primary keys because the method of doing so differs between DB systems and DBUtil is not actually that aware what DBMS you are using.
To do this you will have to construct the query manually in your migration and use DB::query() to execute it.
In case anyone else is faced with the same task, here is what I ended up doing. My database is MySQL, the syntax may have to be changed if you're using a different DBMS. My original primary key was an auto-incrementing column named id.
class Modify_TableName_To_Temporal
{
public function up()
{
\DBUtil::add_fields('tablename',array(
'temporal_start'=>array('constraint'=>11, 'type'=>'int','default'=>0),
'temporal_end'=>array('constraint'=>11, 'type'=>'int','default'=>2147483647),
));
\DB::query('ALTER TABLE tablename MODIFY id int, DROP PRIMARY KEY')->execute();
\DB::query('ALTER TABLE tablename ADD PRIMARY KEY (id, temporal_start, temporal_end), MODIFY id int auto_increment')->execute();
}
public function down()
{
\DB::query('ALTER TABLE tablename MODIFY id int, DROP CONSTRAINT primary')->execute();
\DB::query('ALTER TABLE tablename ADD PRIMARY KEY (id), MODIFY id int auto_increment')->execute();
\DBUtil::drop_fields('tablename',array('temporal_start','temporal_end'));
}
}
Related
I have recently been using PostgreSQL rather than SQL, so finding a lot of little nuances between the two.
I want to be able to make a string value unique in a table, so using the EF code first fluent API, I have this code.
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity<MyTable>()
.HasIndex(u => u.UniqueValue)
.IsUnique();
base.OnModelCreating(modelBuilder);
}
When creating a migration, it will generate this.
protected override void Up(MigrationBuilder migrationBuilder)
{
migrationBuilder.CreateIndex(
name: "IX_MyTable_UniqueValue",
table: "MyTable",
column: "UniqueValue",
unique: true);
}
This will then add the index to the PostgreSQL table, and work when the word is of the same case.
e.g. Try and insert "Hello" twice, and it will not work.
It does allow for variations of the word though, so I can insert "Hello", "HEllo", "HELlo", etc...
It looks like it is possible to force the case on the index in PostgreSQL using something like
CREATE UNIQUE INDEX UniqueValue ON MyTable (UPPER(UniqueValue));
However I am not sure how to do this via EF Fluent API and create the migration from that?
It seems like for now you'll have to set up a raw SQL migration. Support for that still hasn't been added (yet). You could also set up a generated (computed) column that holds the result of upper(UniqueValue), then add a unique index on that.
There's no way to add an expression-based unique constraint or to add the expression to an existing unique index key. You can build a new index using your definition as is:
CREATE UNIQUE INDEX UniqueValue ON MyTable (UPPER(UniqueValue));
Or add an exclusion constraint which ends up doing pretty much the same (as of now, quite far from being supported in EF):
create table test(txt text);
alter table test
add constraint case_insensitive_unique
exclude using gist(upper(txt) with =);
insert into test(txt) select 'hello';
--INSERT 0 1
insert into test(txt) select 'Hello';
--ERROR: conflicting key value violates exclusion constraint "case_insensitive_unique"
--DETAIL: Key (upper(txt))=(HELLO) conflicts with existing key (upper(txt))=(HELLO).
Demo
I would like to have a table with a string column as a primary key without having to use raw SQL syntax.
Here's my fluent "preparation":
static func prepare(_ database: Database) throws {
try database.create("roles") { roles in
roles.id("name")
roles.string("readable_name")
}
}
According to both my tests and the docs, resulting query will be similar to:
CREATE TABLE `roles` (`name` INTEGER PRIMARY KEY NOT NULL, `readable_name` TEXT NOT NULL)
I could not, so far, find a way to have a string (TEXT, VARCHAR, ...) as a primary key without raw SQL syntax and i would like to know whether it's possible to do it or not using the fluent query builder which comes with vapor.
Support for ID types besides INT was added in Fluent 2.
https://docs.vapor.codes/2.0/fluent/model/#id-type
Someone else asked a similar question here: How can I use EF6 to update a many to many table
I mention that up front because I couldn't get any of the solutions given to work.
I also studied the solution give on Code Project: http://www.codeproject.com/Tips/893609/CRUD-Many-to-Many-Entity-Framework, but this doesn't work for me either.
I'm trying to keep this as simple as possible.
I have two tables: dbo.Teacher and dbo.Student. Each has an "ID" column that servers as a primary key. I also have a third table called dbo.StudentTeacher which has exactly two columns, both are non-nullable and foreign keyed to the previous two tables; in other words, it establishes a many-to-many relationship between teachers and students. As expected, the EDMX designed shows only dbo.Student and dbo.Teacher and infers the relationship between them.
Here is a script for the above; there is nothing else in the database.
CREATE TABLE dbo.Teacher
(
Id INT NOT NULL PRIMARY KEY,
Name VARCHAR(MAX)
);
CREATE TABLE dbo.Student
(
Id INT NOT NULL PRIMARY KEY,
Name VARCHAR(MAX)
);
CREATE TABLE dbo.TeacherStudent
(
TeacherId INT NOT NULL FOREIGN KEY REFERENCES Teacher(Id),
StudentId INT NOT NULL FOREIGN KEY REFERENCES Student(Id)
);
INSERT INTO Teacher(Id, Name)
VALUES
(101, 'Tom');
INSERT INTO Student(Id, Name)
VALUES
(201, 'Sue'),
(202, 'Stan');
INSERT INTO TeacherStudent(TeacherId, StudentId)
VALUES
(101, 201);
Now that I've established my data structures, I want to accomplish a very simple task. From the script above, you can see that we have one teacher named "Tom" who has a student named "Sue". We also have a student named "Stan" with no teacher. My task is to modify the database so that Sue is no longer Tom's student and Stan becomes Tom's student.
To accomplish this, I wrote the following code:
class Program
{
static void Main(string[] args)
{
using (var entities = new TestEntities())
{
// There is only one teacher in the system.
Teacher teacher = entities.Teachers.Single();
// This teacher has a student #201: Sue.
// I want to replace her with student #202: Stan.
teacher.Students.Clear();
teacher.Students.Add(new Student() { Id = 202 });
entities.SaveChanges();
}
}
}
It looks very simple: clear the students associated with Tom and then add Stan as Tom's student. However, when I run the code, I get the following error: Unable to update the EntitySet 'TeacherStudent' because it has a DefiningQuery and no <DeleteFunction> element exists in the <ModificationFunctionMapping> element to support the current operation.
I tried simplifying the problem by trying to just remove Sue from being Tom's student without adding Stan, and I get the exact same error message.
As I understand, this error normally occurs when Entity Framework doesn't have enough information to do what you want it to do, but I really can't see what's missing. There are two simple tables with a join table between them and I need to be able to change which rows are related to which other rows.
I should also note that if I'm not mistaken, the change that I wish to make in this example should affect only the dbo.TeacherStudent table; the other two tables should not be touched.
Okay, after some more Google-Fu, I figured it out.
Even tho the join table must have only two columns with each column foreign keyed to the two tables to be related, the join table still needs a primary key, which can be a composite of the two foreign keys.
Thus, dbo.TeacherStudent should be created with this:
CREATE TABLE dbo.TeacherStudent
(
TeacherId INT NOT NULL FOREIGN KEY REFERENCES Teacher(Id),
StudentId INT NOT NULL FOREIGN KEY REFERENCES Student(Id),
PRIMARY KEY(TeacherId, StudentId)
);
In EF Code First, we can create one-to-one relationship by coding like this:
public class User
{
public int UserID {get;set;}
public string Name {get;set;}
public int UserDetailID {get;set;}
public UserDetail Detail {get;set;}
}
public class UserDetail
{
public int UserDetailID {get;set;}
public string Address {get;set:}
public int UserID {get;set;}
public User User {get;set;}
}
However, when I tried to create the same relationship by using EF Database first in visual studio 2012, I got in trouble. Here is my code:
CREATE TABLE [dbo].[Users] (
[UserID] UNIQUEIDENTIFIER CONSTRAINT [DF_Users_UserID] DEFAULT (newid()) NOT NULL,
[UserDetailID] UNIQUEIDENTIFIER NOT NULL,
[Name] NVARCHAR (50) NOT NULL,
CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([UserID] ASC),
CONSTRAINT [FK_Users_UserDetails] FOREIGN KEY ([UserDetailID]) REFERENCES [UserDetails]([UserDetailID])
);
CREATE TABLE [dbo].UserDetails] (
[UserDetailID] UNIQUEIDENTIFIER CONSTRAINT [DF_UserDetails_UserDetailID] DEFAULT (newid()) NOT NULL,
[UserID] UNIQUEIDENTIFIER NOT NULL,
[Address] NVARCHAR(100) NOT NULL,
CONSTRAINT [PK_UserDetails] PRIMARY KEY CLUSTERED ([UserDetailID] ASC),
CONSTRAINT [FK_UserDetails_Users] FOREIGN KEY ([UserID]) REFERENCES [dbo].[Users] ([UserID])
The error message is something like
"Error 2 SQL01767: Foreign key 'FK_Users_UserDetails' references invalid table 'UserDetails'.
I think the reason for this error probably be when it tries to reference the foreign key "UserDetailID", it finds that it hasn't been created yet. But I don't know how to fix this, and I don't even know this is the way to do it, I know doing one-to-one relationship with EF is tricky, or some people even says it's impossible. Can anyone give me any suggestion? Thank you.
Update: Just to clarify my case, I am trying to design the database in visual studio 2012 database project, then publish it to the SQL server, afterward, create/update my .edmx file from the database in SQL server. I am not sure about how to create a one-to-one relationship that the EF can recognize correctly and create the right classes in .edmx file.
Creating a 1:1 relationship is not that tricky and certainly not impossible, although it is not a particularly common requirement and in this case I can't see why you would want it? If people are saying this then you are talking to the wrong people.
Anyhow using SQL queries as you seem to be is not to do with EF, you are just working directly with the database, In the first CREATE you are trying to add the constraint but you haven't created the other table yet... As you mentioned in your question.
I think you need to create both tables first and then add the constraint with ALTER TABLE.
Additionally searching SO for questions about 1:1 turns up quite a lot so I suggest you do that.
EDIT: So using a database project (I only have VS Express so I don't have those) you want to create a "1:1" relationship using SQL and then add an Entity Data Model to a (probably different) project which references the database and automatically create 1:1 relationship?
That is a whole different story unfortunately. When I was talking about possibility to create 1:1 that was in reference to EF only and not to databases as such. It is actually very difficult/impossible as you said to create 1:1 in SQL. I think that it makes sense that in order to insert into a 1:1 realationship you would need to somehow insert into both tables at exactly the same time or fiddle about with disabling constraints briefly when adding rows.
In general there are a few different option.
Don't split the tables unnecessarily. In true 1:1 all data is required so the only reason to split is for performance reasons (e.g partioning) which I would avoid in this case.
Map multiple table to a single entity as show here.
Create a 1:0..1 relationship and enforce you own requirements in the application.
In either option 2 or 3 you can use the following SQL to create a relationship which uses the same PK on the second table as the FK in the relationship.
CREATE TABLE [dbo].[Users] (
[UserID] UNIQUEIDENTIFIER CONSTRAINT [DF_Users_UserID] DEFAULT (newid()) NOT NULL,
[Name] NVARCHAR (50) NOT NULL,
CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED ([UserID] ASC),
);
CREATE TABLE [dbo].[UserDetails] (
[UserID] UNIQUEIDENTIFIER NOT NULL,
[Address] NVARCHAR(100) NOT NULL,
CONSTRAINT [PK_UserDetails] PRIMARY KEY CLUSTERED ([UserID] ASC),
CONSTRAINT [FK_UserDetails_Users] FOREIGN KEY ([UserID]) REFERENCES [dbo].[Users] ([UserID]) ON DELETE CASCADE
);
I suggest you also use store generated identity as well where you can.
Just remove UserDetailID from the UserDetail table and make UserID both primary key and a foreign key to the UserID column of the User table.
This the correct way to make 1:1 relationships in a database and EF recognizes it and maps the entities appropriately with database-first approach.
The question is a couple years old.. and the ef version wasn't stated.. but one answer is to remove UserDetailID from both tables. UserID should be the only primary key on both tables.
the 'unqieidentifier' (GUID) data type shouldn't pose an issue (opposed to using INT), but you certainly don't want to populate it with newId..
I would like to know how to use trim function when declaring primary key in db2.
For example, in table Employee(name,id) how to restrict the usage of these two insert statements:
insert into Employee(name,id) values (jay,1);
insert into Employee(name,id) values (jay,1);
In the above statements both name and id are primary keys.
maybe you mean unique? if so, well you can easily solve this problem, all you have to do, is to create a primary key on bouth fields ;-)
something like this:
alter table Employee add constraint Employee_pk primary key (name, id)