Study on the use and effect of foreignkeyconstraint foreign KEY constraint [turn]

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da.selectcommand.commandtext="Select Au_id,au_fname,au_lname from authors"; Da. Fill (DS,"Author"); Da.SelectCommand.CommandText="Select au_id,title_id from titleauthor"; Da. Fill (DS,"titleauthor"); Da.SelectCommand.CommandText="Select Title_id,title from titles"; Da. Fill (DS,"Titles"); //Ds. tables["Titles"]. columns["title_id"]. Unique=true; Ds. tables["Titles"]. columns["title_id"]. Allowdbnull=false; Ds. tables["Titles"]. primarykey=NewDatacolumn[]{ds. tables["Titles"]. columns["title_id"]}; //Ds. tables["Author"]. columns["au_id"]. Unique=true; Ds. tables["Author"]. columns["au_id"]. Allowdbnull=false; Ds. tables["Author"]. primarykey=NewDatacolumn[]{ds. tables["Author"]. columns["au_id"]}; //Ds. tables["titleauthor"]. primarykey=NewDatacolumn[]{ds. tables["titleauthor"]. columns["au_id"], ds. tables["titleauthor"]. columns["title_id"]}; //Defining ConstraintsForeignKeyConstraint fk1=NewForeignKeyConstraint ("Authorstitleauthor"Ds. tables["Author"]. columns["au_id"], ds. tables["titleauthor"]. columns["au_id"]); Ds. tables["titleauthor"].    Constraints.add (FK1); ForeignKeyConstraint FK2=NewForeignKeyConstraint ("Titlestitleauthor"Ds. tables["Titles"]. columns["title_id"], ds. tables["titleauthor"]. columns["title_id"]); Ds. tables["titleauthor"].    Constraints.add (FK2);  This. datagrid1.datasource=ds;  This. datagrid1.datamember="titleauthor";

After you set the foreign key, when you edit a record in titleauthor on the DataGrid, the edited record cannot be updated and added when it is not in the title and author.

Study on the use and effect of foreignkeyconstraint foreign KEY constraint [turn]