Updating child records ado


03-May-2015 05:48

We have already seen how to create a foreign key using this dialog box. When a relationship has been established between two tables, you can ask the database engine to observe some rules between the tables on one hand and among the records on the other hand. To visually manage referential integrity, you can use the Foreign Key Relationships dialog box. To access it, first open the child table in the design view. Click += new Event Handler(Create Tables); btn Select Records = new Button(); btn Select Records. Data relationships allow records from one object to be available to other objects. When a relationship has been established between two tables, one of the concerns is to plan what would happen if a record from a parent table is deleted or moved. Two combo boxes would appear: Delete Rule and Update Rule These two combo boxes have the same four options: The opttions can be set either visually or programmatically. Here is an example: void Create Table(object sender, Event Args e) { using (Sql Connection connection = new Sql Connection("Data Source=(local);" + "Database='People';" + "Integrated Security=yes;")) { Sql Command command = new Sql Command("CREATE TABLE Persons " + "( " + "Person ID int identity(1,1) PRIMARY KEY NOT NULL, " + "First Name nvarchar(20), " + "Last Name nvarchar(20) NOT NULL, " + " You would follow the same approach for the update.

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As reviewed already, if you had not yet created a foreign key on the table that was displaying, the dialog box would appear empty. Form { Button btn Create Tables; Button btn Select Records; Data Grid View dgv Persons; public Exercise() { Initialize Component(); } void Initialize Component() { btn Create Tables = new Button(); btn Create Tables. Consider the following tables: using System; using System. Of course, before setting these rules, you must have created the relationship. Once this is done, in the Foreign Key Relationships dialog box, expand INSERT And UPDATE Specification.

Referential integrity is the ability to take appropriate actions when tables or records involved in a relationship are affeected.

To assist you with this aspect of database management, Both Microsoft SQL Server and Transact-SQL provide various tools. Click += new Event Handler(Select Records); dgv Persons = new Data Grid View(); dgv Persons.