barcode generator vb.net download The UPDATE Statement in Software

Encode QR-Code in Software The UPDATE Statement

The UPDATE Statement
Decoding Quick Response Code In None
Using Barcode Control SDK for Software Control to generate, create, read, scan barcode image in Software applications.
QR-Code Creation In None
Using Barcode drawer for Software Control to generate, create QR Code image in Software applications.
The UPDATE statement, shown in Figure 10-6, modifies the values of one or more columns in selected rows of a single table. The target table to be updated is named in the statement, and you must have the required permission to update the table as well as each of the individual columns that will be modified. The WHERE clause selects the rows of the table to be modified. The SET clause specifies which columns are to be updated and calculates the new values for them. Here is a simple UPDATE statement that changes the credit limit and salesperson for a customer: Raise the credit limit for Acme Manufacturing to $60,000 and reassign the company to Mary Jones (employee number 109).
QR Code JIS X 0510 Decoder In None
Using Barcode reader for Software Control to read, scan read, scan image in Software applications.
Printing Quick Response Code In C#
Using Barcode generator for Visual Studio .NET Control to generate, create QR Code 2d barcode image in .NET framework applications.
UPDATE CUSTOMERS SET CREDIT_LIMIT = 60000.00, CUST_REP = 109 WHERE COMPANY = 'Acme Mfg.'; 1 row updated.
QR Code JIS X 0510 Creator In .NET
Using Barcode generation for ASP.NET Control to generate, create QR Code image in ASP.NET applications.
Make QR Code ISO/IEC18004 In .NET Framework
Using Barcode printer for .NET Control to generate, create QR Code 2d barcode image in Visual Studio .NET applications.
PART III
QR Code Drawer In VB.NET
Using Barcode drawer for .NET Control to generate, create Quick Response Code image in .NET applications.
ECC200 Maker In None
Using Barcode printer for Software Control to generate, create Data Matrix image in Software applications.
In this example, the WHERE clause identifies a single row of the CUSTOMERS table, and the SET clause assigns new values to two of the columns in that row. The WHERE clause is exactly the same one you would use in a DELETE or SELECT statement to identify the row. In fact, the search conditions that can appear in the WHERE clause of an UPDATE statement are exactly the same as those available in the SELECT and DELETE statements. Like the DELETE statement, the UPDATE statement can update several rows at once with the proper search condition, as in this example: Transfer all salespeople from the Chicago of ce (number 12) to the New York of ce (number 11), and lower their quotas by 10 percent.
Encoding ANSI/AIM Code 128 In None
Using Barcode creator for Software Control to generate, create Code-128 image in Software applications.
Paint EAN / UCC - 13 In None
Using Barcode generator for Software Control to generate, create USS-128 image in Software applications.
UPDATE SALESREPS SET REP_OFFICE = 11, QUOTA = .9 * QUOTA WHERE REP_OFFICE = 12; 3 rows updated.
Making ANSI/AIM Code 39 In None
Using Barcode generator for Software Control to generate, create Code 39 image in Software applications.
GTIN - 13 Drawer In None
Using Barcode generator for Software Control to generate, create EAN13 image in Software applications.
UPDATE table-name SET
Leitcode Drawer In None
Using Barcode drawer for Software Control to generate, create Leitcode image in Software applications.
Generate Bar Code In None
Using Barcode encoder for Online Control to generate, create bar code image in Online applications.
column-name = expression ,
Create Bar Code In C#
Using Barcode creator for Visual Studio .NET Control to generate, create barcode image in Visual Studio .NET applications.
Paint DataMatrix In Java
Using Barcode generator for BIRT Control to generate, create DataMatrix image in BIRT applications.
WHERE search-condition
Drawing 2D Barcode In .NET
Using Barcode creation for ASP.NET Control to generate, create Matrix Barcode image in ASP.NET applications.
Barcode Encoder In Java
Using Barcode creation for BIRT reports Control to generate, create bar code image in BIRT applications.
FIGURE 10-6
Scanning UPCA In C#.NET
Using Barcode decoder for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
DataMatrix Reader In Visual C#
Using Barcode reader for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
UPDATE statement syntax diagram
Part III:
Updating Data
In this case, the WHERE clause selects several rows of the SALESREPS table, and the value of the REP_OFFICE and QUOTA columns are modified in all of them. Conceptually, SQL processes the UPDATE statement by going through the SALESREPS table row by row, updating those rows for which the search condition yields a TRUE result and skipping over those for which the search condition yields a FALSE or NULL result. Because it searches the table, this form of the UPDATE statement is sometimes called a searched UPDATE statement. This term distinguishes it from a different form of the UPDATE statement, called a positioned UPDATE statement, which always updates a single row. The positioned UPDATE statement applies only to programmatic SQL and is described in 17. Here are some additional examples of searched UPDATE statements: Reassign all customers served by employee numbers 105, 106, or 107 to employee number 102.
UPDATE CUSTOMERS SET CUST_REP = 102 WHERE CUST_REP IN (105, 106, 107); 5 rows updated.
Assign a quota of $100,000 to any salesperson who currently has no quota.
UPDATE SALESREPS SET QUOTA = 100000.00 WHERE QUOTA IS NULL; 1 row updated.
The SET clause in the UPDATE statement is a list of assignments separated by commas. Each assignment identifies a target column to be updated and specifies how to calculate the new value for the target column. Each target column should appear only once in the list; there should not be two assignments for the same target column. The ANSI/ISO specification mandates unqualified names for the target columns, but some SQL implementations allow qualified column names. There can be no ambiguity in the column names anyway, because they must refer to columns of the target table. The expression in each assignment can be any valid SQL expression that yields a value of the appropriate data type for the target column. The expression must be computable based on the values of the row currently being updated in the target table. In most DBMS implementations, the expression may not include any column functions or subqueries. If an expression in the assignment list references one of the columns of the target table, the value used to calculate the expression is the value of that column in the current row before any updates are applied. The same is true of column references that occur in the WHERE clause. For example, consider this (somewhat contrived) UPDATE statement:
UPDATE SALESREPS SET QUOTA = 400000.00, SALES = QUOTA WHERE QUOTA < 400000.00;
Before the update, Bill Adams had a QUOTA value of $350,000 and a SALES value of $367,911. After the update, his row has a SALES value of $350,000, not $400,000. The order of the assignments in the SET clause is thus immaterial; the assignments can be specified in any order.
10:
Copyright © OnBarcode.com . All rights reserved.