barcode generator in vb.net 2005 Parent/Child Queries in Software

Generating QR Code 2d barcode in Software Parent/Child Queries

Parent/Child Queries
Read Quick Response Code In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
Create QR In None
Using Barcode creation for Software Control to generate, create QR-Code image in Software applications.
The most common multitable queries involve two tables that have a natural parent/child relationship. The query about orders and customers in the preceding section is an example of such a query. Each order (child) has an associated customer (parent), and each customer (parent) can have many associated orders (children). The pairs of rows that generate the query results are parent/child row combinations. You may recall from 4 that foreign keys and primary keys create the parent/ child relationship in a SQL database. The table containing the foreign key is the child in the relationship; the table with the primary key is the parent. To exercise the parent/child relationship in a query, you specify a search condition that compares the foreign key and the primary key. Here is another example of a query that exercises a parent/child relationship, shown in Figure 7-3. List each salesperson and the city and region where they work.
Quick Response Code Recognizer In None
Using Barcode scanner for Software Control to read, scan read, scan image in Software applications.
Denso QR Bar Code Drawer In C#.NET
Using Barcode encoder for VS .NET Control to generate, create QR-Code image in Visual Studio .NET applications.
SELECT NAME, CITY, REGION FROM SALESREPS, OFFICES WHERE REP_OFFICE = OFFICE; NAME -------------Mary Jones Sam Clark Bob Smith Paul Cruz Dan Roberts Bill Adams Sue Smith Larry Fitch Nancy Angelli CITY -----------New York New York Chicago Chicago Chicago Atlanta Los Angeles Los Angeles Denver REGION -------Eastern Eastern Eastern Eastern Eastern Eastern Western Western Western
Draw QR Code 2d Barcode In Visual Studio .NET
Using Barcode creation for ASP.NET Control to generate, create Denso QR Bar Code image in ASP.NET applications.
Print QR Code ISO/IEC18004 In .NET Framework
Using Barcode generation for .NET framework Control to generate, create Denso QR Bar Code image in .NET framework applications.
PART II
QR-Code Generation In Visual Basic .NET
Using Barcode generator for Visual Studio .NET Control to generate, create QR Code JIS X 0510 image in .NET framework applications.
Code 3/9 Generator In None
Using Barcode creation for Software Control to generate, create Code 3/9 image in Software applications.
The SALESREPS (child) table contains REP_OFFICE, a foreign key for the OFFICES (parent) table. This relationship is used to find the correct OFFICES row for each salesperson, so that the correct city and region can be included in the query results. Here s another query involving the same two tables, but with the parent and child roles reversed, as shown in Figure 7-4.
Barcode Printer In None
Using Barcode creation for Software Control to generate, create barcode image in Software applications.
European Article Number 13 Generator In None
Using Barcode creator for Software Control to generate, create GS1 - 13 image in Software applications.
Part II:
Draw Universal Product Code Version A In None
Using Barcode drawer for Software Control to generate, create GS1 - 12 image in Software applications.
USS-128 Creation In None
Using Barcode creator for Software Control to generate, create EAN / UCC - 14 image in Software applications.
Retrieving Data
Make Postnet 3 Of 5 In None
Using Barcode encoder for Software Control to generate, create USPS POSTal Numeric Encoding Technique Barcode image in Software applications.
ANSI/AIM Code 39 Scanner In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
OFFICES Table
GTIN - 13 Generator In .NET Framework
Using Barcode maker for ASP.NET Control to generate, create EAN13 image in ASP.NET applications.
Paint 1D In .NET Framework
Using Barcode generator for ASP.NET Control to generate, create Linear 1D Barcode image in ASP.NET applications.
OFFICE 22 11 12 13 21 CITY Denver New York Chicago Atlanta Los Angeles REGION MGR TARGET SALES $186,042.00 $692,637.00 $735,042.00 $367,911.00 $835,915.00 Western 108 $300,000.00 Eastern 106 $575,000.00 Eastern 104 $800,000.00 Eastern NULL $350,000.00 Western 108 $725,000.00
Create EAN13 In Java
Using Barcode encoder for Java Control to generate, create GTIN - 13 image in Java applications.
Encode Code39 In None
Using Barcode creation for Microsoft Word Control to generate, create USS Code 39 image in Word applications.
SALESREPS Table EMPL_NUM NAME
EAN / UCC - 13 Reader In Java
Using Barcode scanner for Java Control to read, scan read, scan image in Java applications.
Paint Bar Code In None
Using Barcode encoder for Font Control to generate, create barcode image in Font applications.
105 109 102 106 104 101 110 108 103 107 Bill Adams Mary Jones Sue Smith Sam Clark Bob Smith Dan Roberts Tom Snyder Larry Fitch Paul Cruz Nancy Angelli
AGE REP_OFFICE
37 31 48 52 33 45 41 62 29 49 13 11 21 11 12 12 NULL 21 12 22
TITLE
Sales Rep Sales Rep Sales Rep VP Sales Sales Mgr Sales Rep Sales Rep Sales Mgr Sales Rep Sales Rep
Query Results NAME CITY REGION
FIGURE 7-3
A parent/child query with the OFFICES and SALESREPS tables
SALESREPS Table EMPL_NUM NAME 105 109 102 106 104 101 110 108 103 107 Bill Adams Mary Jones Sue Smith Sam Clark Bob Smith Dan Roberts Tom Snyder Larry Fitch Paul Cruz Nancy Angelli
AGE 37 31 48 52 33 45 41 62 29 49
REP_OFFICE 13 11 21 11 12 12 NULL 21 12 22
TITLE Sales Rep Sales Rep Sales Rep VP Sales Sales Mgr Sales Rep Sales Rep Sales Mgr Sales Rep Sales Rep
OFFICES Table OFFICE CITY 22 11 12 13 21 Denver New York Chicago Atlanta Los Angeles
REGION
TARGET
Query Results CITY NAME
TITLE
Western 108 $300,000.00 Eastern 106 $575,000.00 Eastern 104 $800,000.00 Eastern NULL $350,000.00 Western 108 $725,000.00
FIGURE 7-4
A different parent/child query with the OFFICES and SALESREPS tables
7:
Multitable Queries (Joins)
List the offices and the names and titles of their managers.
SELECT CITY, NAME, TITLE FROM OFFICES, SALESREPS WHERE MGR = EMPL_NUM; CITY -----------Chicago Atlanta New York Denver Los Angeles NAME -----------Bob Smith Bill Adams Sam Clark Larry Fitch Larry Fitch TITLE ---------Sales Mgr Sales Rep VP Sales Sales Mgr Sales Mgr
PART II
The OFFICES (child) table contains MGR, a foreign key for the SALESREPS (parent) table. This relationship is used to find the correct SALESREPS row for each salesperson, so that the correct name and title of the manager can be included in the query results. SQL does not require that the matching columns be included in the results of a multitable query. They are often omitted in practice, as in the two preceding examples. That s because primary keys and foreign keys are often ID numbers (such as the office numbers and employee numbers in the examples), which humans find hard to remember, while the associated names (cities, regions, names, titles) are easier to understand. It s quite common for ID numbers to be used in the WHERE clause to join two tables, and for more descriptive names to be specified in the SELECT clause to generate columns of query results.
Copyright © OnBarcode.com . All rights reserved.