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Now we can insert some data into the new table. Example B.27. in .NET Maker PDF417 in .NET Now we can insert some data into the new table. Example B.27.




How to generate, print barcode using .NET, Java sdk library control with example project source code free download:
Now we can insert some data into the new table. Example B.27. using visual .net toincoporate pdf417 with asp.net web,windows application iPhone mysql> INSE Visual Studio .NET pdf417 2d barcode RT INTO dog(name,owner,breed, sex, birth, death) -> VALUES("Fido","Mr. Jones", "Mutt", "M", "2004-11-12", "2006-04-02"); Query OK, 1 row affected (0.

09 sec). B.3.4. Creating a Key In real life, .net framework pdf417 people can be identified by Social Security numbers, driver"s license numbers, and employee numbers; books can be identified by ISBN numbers; and a Web store order can be identified by a purchase order number. These identification numbers must be unique so that no two people have the same Social Security number, no two books have the same ISBN number, and so on.

Keys are used to uniquely identify a record in a table. There are two types of keys: primary keys and foreign keys..

Primary Keys Each table typ .net vs 2010 PDF 417 ically has a primary key. Primary keys are used to uniquely identify a record in the database.

They must be unique, never change, occur only once per table, and are normally numeric types. You can choose to manually generate this unique number for each record or let the database do it for you. If you let the database generate the primary key, it will generate a unique number, given a starting value (e.

g., 1) and then for each new record, increment that number by 1. Even if a record is deleted, that number is never recycled.

The database increments its internal counter, guaranteeing that each record will be given a unique "key." To set a field as a primay key, use the attribute PRIMARY KEY (field_name), and to tell the database to automatically create the unique number, use the AUTO_INCREMENT attribute following the field definition. The primary key cannot be null.

The following two examples describe a table called categories where the primary key is called CategoryID. It will automatically be incremented each time a new category is added to the table..

Example B.28. mysql> USE Visual Studio .NET PDF417 northwind; Database changed mysql> DESCRIBE categories; +--------------+-------------+------+-----+---------+----------------+ . Field Type Null Key Default Extra +--------------+-------------+------+-----+---------+----------------+ CategoryID int(11) . PRI NULL auto_increment CategoryName varchar(15) . MUL Description longtext YES NULL Picture longblob YES NULL +------------ barcode pdf417 for .NET --+-------------+------+-----+---------+----------------+ 4 rows in set (0.09 sec).

Explanation The CategoryID .net framework PDF417 is the primary key, an integer of up to 11 digits, which will be incremented by 1, initially set to NULL (no value). The first time a record is inserted into the database, the value will be 1.

Example B.29..

mysql> SELECT CategoryID, CategoryName FROM categories; +------------+----------------+ CategoryID CategoryName +------------+----------------+ 1 . Beverages 2 . Condiments 3 . Confections 4 . Dairy Products 5 . Grains/Cereals 6 . Meat/Poultry 7 . Produce 8 . Seafood +------------ +----------------+ 8 rows in set (0.16 sec). Explanation The primary ke y is called CategoryID. It is used to uniquely identify the different categories in this table from the northwind database. When a new category is added to the table, the CategoryID will be automatically incremented by 1.

. Foreign Keys If a primary k ey is referenced in another table, it is called a foreign key. Foreign keys are used to create relation between tables. In the following example, two tables are described that both reference the CategoryID key, although it is primary in one and foreign in the other.

Example B.30..

Code View: mys visual .net barcode pdf417 ql> DESCRIBE categories; +--------------+-------------+------+-----+---------+----------------+ . Field Type Null Key Default Extra +--------------+-------------+------+-----+---------+----------------+ 1 CategoryID int(11) . PRI NULL auto_increment CategoryName varchar(15) . MUL Description longtext YES NULL Picture longblob YES NULL +------------ PDF 417 for .NET --+-------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec) mysql> DESCRIBE products; +----------------+--------------+-----+-----+--------+---------------+ .

Field Type Null Key Default Extra +------------ ----+--------------+-----+-----+--------+---------------. ProductID int(11) . PRI NULL auto_increment ProductName varchar(40) . MUL SupplierID int(11) . YES MUL NULL 2 . CategoryID int(11) . YES MUL NULL QuantityPerUnit varchar(20) . YES NULL UnitPrice decimal(19,4). YES NULL UnitsInStock smallint(6) . YES NULL UnitsOnOrder smallint(6) . YES NULL ReorderLevel smallint(6) . YES NULL Discontinued tinyint(4) . 0 . +------------ pdf417 for .NET ----+--------------+-----+-----+--------+---------------+ 10 rows in set (0.00 sec).

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