what axxess keys used for

When operating the Oracle view through DML, a very important condition is that the base table to be operated must be a key-preserved table.So what is the key-preserved table? Oracle defines it:A table is key preserved if every key of the table can also be a key of the result of the join.It is not necessary that the key or keys of a table be selected for it to be key preserved. It is sufficient that if the k

What are some of the techniques commonly used in Photoshop? 1. Quickly open file Double-click the background space in Photoshop (the default is the gray display area) to open the Browse window for the selected file. 2. Change the canvas color freely Select the Paint Bucket tool and hold down SHIFT and click on the edge of the canvas to set the canvas background to the currently selected foreground c

, characteristics and technical characteristics of history. ASCII Character Set 1. The origin of the name ASCII (American Standard Code for Information Interchange, American Information Interchange standard codes) is a computer coding system based on the Roman alphabet. 2. Features It is mainly used to display modern English and other Western European languages. It is the most common single byte coding system today and is equivalent to ISO 646.

HTML5 now more and more fire, many people want to learn HTML5, but HTML5 than the old version of the new form elements, now let's look at what the new form elements. HTML5 What are the new commonly used form elements? How are they used separately? This chapter describes the following new form elements: Datalist;keygen

What is the best code reading or editing tool you have used? Besides source insight16 answersAnswer 1: Intellij is rated as the best IDE and is well received abroad. Can Quickly locate methods in the class. In addition, the Integrated UML can produce UML diagrams for a class and view the full picture of a class. Its multi-window function can be compiled in different windows. It is more prominent under multi

What if the win7 System Restore button turns gray and cannot be used? 1, single hit open Win7 computer Start menu, and then into the control Panel; 2, in the interface of the Control Panel, click into the system security-system-management tool service, then we find Windows Backup service in the Open service window, and click to start the service; 3, if the above method can not solve the pro