.net pdf 417

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When doing problems of this kind, remember to use the capacitive reactance values for X C, and not the capacitance values This means that, if you are given the capacitance, you must use the formula for X C in terms of capacitance and frequency and then calculate the phase angle You should get angles that come out negative or zero This indicates that they re RC phase angles rather than RL phase angles (which are always positive or zero)

CREATE TABLE invoice ( invoiceNumber char(10) CONSTRAINT PKinvoice PRIMARY KEY, invoiceStatus varchar(10) CONSTRAINT invoice$invoiceStatus ) CHECK (invoiceStatus in ('Open','Closed')) CREATE TABLE invoiceItem ( invoiceNumber char(10), invoiceItemNumber int, CONSTRAINT PKinvoiceItem PRIMARY KEY (invoiceNumber, invoiceItemNumber) )

15 Both of these parameters are optional, so you can use the save verb without either,

If you don t take the time to add the foreign key constraint, then the value for orderNumber in the orderItem table isn t bound to any domain of values. It could be Hello! for all that matters, even if that value didn t get created in the order table. The problem is that no matter the intentions of the non data tier implementers, it s difficult to test for all possible scenarios, and impossible to stop a DBA from messing up the data by accident. A good example of the kinds of problems you can run into is a query against a child, such as an invoice line item. A query against this table should give consistent results whether or not you include the invoice in the query. So executing a query like the following

Problem 14-4 Suppose the capacitive reactance in an RC circuit is 3800 and the resistance is 7400 What is the phase angle Find the ratio X C /R = 3800/7400 The calculator display should show you something like 0513513513 Find the arctangent, or tan 1, getting a phase angle of 2718111109 on the calculator display Round this off to 2718 Problem 14-5 Suppose an RC circuit works at a frequency of 350 MHz It has a resistance of 130 and a capacitance of 150 pF What is the phase angle First, find the capacitive reactance for a capacitor of 150 pF at 350 MHz Convert the capacitance to microfarads, getting C = 0000150 F Remember that microfarads go with megahertz (millionths go with millions to cancel each other out) Then:

in which case TextEdit prompts the user to enter the filename and choose the folder path if the document has never been saved That s the behavior we ll use here, so add a save the front document statement before the final end tell statement in the script, as shown in boldface here:

Uniqueness constraints to make sure that the set of values for some column or columns only have unique values Filtered indexes to implement selective uniqueness (and performance, but this isn t a performance-tuning chapter) Foreign key constraints to make certain that related values have matches Check constraints to implement checks on the same row, as well as checks on other tables when you want them to happen row by row Triggers for everything else you need to validate in the table, as well as introducing side effects to a query They re seldom used as they re rarely needed, but they re tools that you can use on occasion Sadly this topic also becomes a polarizing political topic as well There are many application developers who ll be annoyed that you want to use constraints to manage anything.

They ll become incensed at the errors that are sent to their client by your constraints, and will demand their removal Even though your goal is to only use constraints to manage never-occurring errors, the fact is that they weren t prepared for bugs in the application code that allow errors to occur This is a defining point in your career when you can, while making them feel good about themselves, explain why this is spurious reasoning There are two reasons why this reasoning is less than sound First, if the errors are not supposed to occur, nobody should notice your constraints in the first place Second, you can t stop all errors from happening SQL Server could encounter a hardware glitch and an error might occur.