C＃如何创建现有表列的主键

Question

I would like to ask for your help. The problem is that I am trying to relate two tables so I need to create primary keys on the tables each "id" columns but I am getting an error on this line

ds.Relations.Add(dr);

Error:

This constraint cannot be enabled as not all values have corresponding parent values.

(original error in Spanish = No se puede habilitar esta restricción ya que todos los valores no tienen los valores primarios correspondientes. )

What am I doing wrong?

OdbcDataAdapter sdata = new OdbcDataAdapter("SELECT * FROM componentes WHERE nombre_componente ILIKE '%" + buscar + "%'", conn);
OdbcDataAdapter sdata2 = new OdbcDataAdapter("SELECT * FROM proveedores WHERE nombre_empresa ILIKE '%" + buscar + "%'", conn);

DataSet ds = new DataSet();

DataTable dtbl = new DataTable("dtbl");
DataTable dtbl2 = new DataTable("dtbl2");

sdata.Fill(dtbl);
sdata2.Fill(dtbl2);

ds.Tables.Add(dtbl);
ds.Tables.Add(dtbl2);

dtbl.PrimaryKey = new DataColumn[] { dtbl.Columns["id"] };
dtbl2.PrimaryKey = new DataColumn[] { dtbl2.Columns["id"] };

DataRelation dr = new DataRelation("provcomp",
                ds.Tables["dtbl"].Columns["id_prov_comp"],
                ds.Tables["dtbl2"].Columns["id"]);

ds.Relations.Add(dr);
ds.AcceptChanges();

Thanks in advance.

Answer 1

The problem here is your data. You're adding a primary key to each table and then attempting to link them with a foreign key.

However, from the error message you are receiving, it sounds like you are attempting to link dtbl to an id from dtbl2 which does not exist.

I would try to do a SQL query to find out where your problem records lie and then choose to either add a "parent", change the parent or delete the record.

SELECT * FROM componentes WHERE id_prov_comp NOT IN (SELECT ID FROM proveedores )

Answer 2

The primary keys are ok - you already successfully created them with the following lines:

dtbl.PrimaryKey = new DataColumn[] { dtbl.Columns["id"] };
dtbl2.PrimaryKey = new DataColumn[] { dtbl2.Columns["id"] };

The problem is (as indicated by the exception) in the DataRelation . DataRelation is the equivalent of the database FK (foreign key). The signature of the used constructor looks like this:

public DataRelation(
    string relationName,
    DataColumn parentColumn,
    DataColumn childColumn
)

I think what you did wrong is specifying the wrong columns - parentColumn should point to the table being referenced while childColumn - the table referencing it.

Simple change it to:

DataRelation dr = new DataRelation("provcomp",
    ds.Tables["dtbl2"].Columns["id"],
    ds.Tables["dtbl"].Columns["id_prov_comp"]);

and if they are really related correctly, the problem should be solved.

Edit: In case the parent table does not contain all the keys from the child table, you might consider using this constructor overload and pass createConstraints = false , which will prevent the exception, but note that some child records will not to find their parent record.

DataRelation dr = new DataRelation("provcomp",
    ds.Tables["dtbl2"].Columns["id"],
    ds.Tables["dtbl"].Columns["id_prov_comp"],
    false);

Answer 3

The parent column (that is primary key) must come before the child column (that is foreign key). Try this:

DataRelation dr = new DataRelation("provcomp",
            ds.Tables["dtbl2"].Columns["id"],
            ds.Tables["dtbl"].Columns["id_prov_comp"]);