barcode generator vb.net download PART III in Software

Encoder QR Code JIS X 0510 in Software PART III

PART III
Read QR-Code In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
QR-Code Generation In None
Using Barcode creator for Software Control to generate, create Denso QR Bar Code image in Software applications.
SET CONSTRAINTS quota_totals DEFERRED; INSERT INTO SALESREPS (EMPL_NUM, NAME, REP_OFFICE, HIRE_DATE, QUOTA, SALES) VALUES (:num, :name, :office_num, :date, :amount, 0); UPDATE OFFICES SET TARGET = TARGET + :amount WHERE (OFFICE = :office_num); COMMIT;
Scan QR In None
Using Barcode recognizer for Software Control to read, scan read, scan image in Software applications.
QR-Code Maker In C#.NET
Using Barcode creator for .NET Control to generate, create QR image in Visual Studio .NET applications.
After the COMMIT statement ends the transaction, the quota_totals constraint is reset back into IMMEDIATE mode because of the INITIALLY IMMEDIATE specification. If there were more work to be done after the UPDATE statement before the end of the transaction, you could manually set the constraint back into IMMEDIATE mode using this statement:
QR Code JIS X 0510 Drawer In .NET
Using Barcode generation for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
QR Code JIS X 0510 Generation In Visual Studio .NET
Using Barcode creation for VS .NET Control to generate, create Quick Response Code image in Visual Studio .NET applications.
SET CONSTRAINTS quota_totals IMMEDIATE;
QR-Code Drawer In Visual Basic .NET
Using Barcode creation for .NET Control to generate, create Quick Response Code image in VS .NET applications.
USS Code 128 Maker In None
Using Barcode drawer for Software Control to generate, create Code 128C image in Software applications.
You can set the same mode for several different constraints by including the constraint names in a comma-separated list:
Barcode Drawer In None
Using Barcode drawer for Software Control to generate, create barcode image in Software applications.
Paint UCC - 12 In None
Using Barcode generation for Software Control to generate, create UCC - 12 image in Software applications.
SET CONSTRAINTS quota_totals, rep_totals IMMEDIATE;
Make Data Matrix ECC200 In None
Using Barcode creation for Software Control to generate, create DataMatrix image in Software applications.
Bar Code Creation In None
Using Barcode maker for Software Control to generate, create barcode image in Software applications.
Finally, you can set the processing mode for all constraints with a single statement:
International Standard Serial Number Creator In None
Using Barcode maker for Software Control to generate, create ISSN - 10 image in Software applications.
Draw Data Matrix 2d Barcode In Visual C#
Using Barcode creation for VS .NET Control to generate, create DataMatrix image in .NET framework applications.
SET CONSTRAINTS ALL DEFERRED;
UCC - 12 Printer In Visual Studio .NET
Using Barcode creator for ASP.NET Control to generate, create UPCA image in ASP.NET applications.
Making Code 3/9 In None
Using Barcode creation for Font Control to generate, create Code39 image in Font applications.
The SQL capabilities for deferred constraint checking form a very comprehensive facility for managing the integrity of a database. As with many capabilities in the SQL standard, individual pieces of the SQL capability were taken from existing SQL implementations,
Bar Code Generation In Visual C#
Using Barcode creator for Visual Studio .NET Control to generate, create bar code image in .NET applications.
Code39 Encoder In Visual Basic .NET
Using Barcode encoder for VS .NET Control to generate, create USS Code 39 image in VS .NET applications.
Part III:
Drawing ECC200 In Visual Basic .NET
Using Barcode creation for .NET Control to generate, create Data Matrix ECC200 image in .NET framework applications.
Barcode Creation In .NET
Using Barcode maker for ASP.NET Control to generate, create barcode image in ASP.NET applications.
Updating Data
and individual pieces have found their way into other implementations since the publication of the standard. IBM s DB2, for example, includes deferred constraint checking capability and supports SQL-style deferability options. Its SET CONSTRAINTS statement, however, differs from the SQL standard. It operates on individual tables in the database, turning on and off the deferral of constraint checking associated with the table contents.
Business Rules
Many of the data integrity issues in the real world have to do with the rules and procedures of an organization. For example, the company that is modeled by the sample database might have rules like these: No customer is allowed to place orders that would exceed the customer s credit limit. The sales vice president must be notified whenever any customer is assigned a credit limit higher than $50,000. Orders may remain on the books for only six months; orders older than six months must be canceled and reentered (assuming the customer still wants them). In addition, there are often accounting rules that must be followed to maintain the integrity of totals, counts, and other amounts stored in a database. For the sample database, these rules probably make sense: Whenever a new order is taken, the SALES column for the salesperson who took the order and for the office where that salesperson works should be increased by the order amount. Deleting an order or changing the order amount should also cause the SALES columns to be adjusted. Whenever a new order is taken, the QTY_ON_HAND column for the product being ordered should be decreased by the quantity of products ordered. Deleting an order, changing the quantity, or changing the product ordered should also cause corresponding adjustments to the QTY_ON_HAND column. These rules fall outside the realm of SQL as defined by the SQL standard and as implemented by many SQL-based DBMS products today. The DBMS takes responsibility for storing and organizing data and ensuring its basic integrity, but enforcing the business rules is the responsibility of the application programs that access the database. Placing the burden of enforcing business rules on the application programs that access the database has several disadvantages: Duplication of effort If six different programs deal with various updates to the ORDERS table, each must include code that enforces the rules relating to ORDERS updates. Lack of consistency If several programs written by different programmers handle updates to a table, they will probably enforce the rules somewhat differently.
11:
Data Integrity
Maintenance problems If the business rules change, the programmers must identify every program that enforces the rules, then locate the code and modify it correctly. Complexity There are often many rules to remember. Even in the small sample database, a program that handles order changes must worry about enforcing credit limits, adjusting sales totals for salespeople and offices, and adjusting the quantities on hand. A program that handles simple updates can become complex very quickly. The requirement that application programs enforce business rules is not unique to SQL. Application programs have had that responsibility since the earliest days of COBOL programs and file systems. However, there has been a steady trend over the years to put more understanding of the data and more responsibility for its integrity into the database itself. In 1986, the Sybase DBMS introduced the concept of a trigger as a step toward including business rules in a relational database. The concept proved to be very popular, so support for triggers began to appear in many SQL DBMS products in the early 1990s, including those of the mainstream enterprise DBMS vendors. Triggers and the enforcement of business rules that they provide have been especially useful in enterprise database environments. When hundreds of application programs are being developed or modified every year by dozens of application programmers, the ability to centralize the definition and administration of business rules can be very useful.
Copyright © OnBarcode.com . All rights reserved.