Examine the following command:CREATE TABLE (prod_id number(4),Prod_name varchar2 (20),Category_id number(30),Quantity_on_hand number (3) INVISIBLE);Which three statements are true about using an invisible column in the PRODUCTS table?（）A. The %ROWTYPE attribute declarations in PL/SQL to access a row will not display the invisible column in the output.B. The DESCRIBE commands in SQL *Plus will not display the invisible column in the output.C. Referential integrity constraint cannot be set on the invisible column.D. The invisible column cannot be made visible and can only be marked as unused.E. A primary key constraint can be added on the invisible column.
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Although the bulk of industry resources and energies have focused on developing the fastest(71)or slickest(72)more and more mindshare is turning to the evolution of the computer interface. Advancements in the areas of input devices,(73)processing and vitual reality could lead to fundamental changes in the way human and computer interact. The technological battlefield of the future will be adding layers between the user and the raw machine to make the(74)as invisible as possible.(75)represents the next evolutionary step for the interface.A．microprocessorB．formatC．structureD．procedure
By saying “Middle children are invisible” in paragraph 3, Lewis means that middle children 。A. have to help their parents to serve dinnerB. get the least attention from the familyC. are often kept away from the dinner tableD. find it hard to keep up with other children
共用题干 GPS Child Locator Lets Parents Know Their WhereaboutsChildren may not like it but a British technology finn has invented an electronic babysitter 一a wristwatch-likedevice that lets parents know where their children are at all times.The GPS Child Locator attaches firmly to a child's wrist and contains a Global Positioning System (GPS),said Matthew Salmon,a spokesman for the manufacturer.______________(46)"It tracks your child.""It only starts working when the device is connected to the child'5 wrist,"Salmon said,"and is very difficult to get off."______________(47)"It would give you a Google Maps image with their exact location,the street name and the zip code."When a child is wearing the device,a parent sends the text message"where are you"and the child'S current location is sent back to a mobile phone or computer.______________(48)" You can also set up a perimeter（界限）, an invisible fence , and if they wander out of this invisible fence which you put on the Internet it will warn you,"Salmon said.______________(49)Salmon said the device is waterproof and shockproof and lasts for three days with a full charge.It will be available in both Britain and the United States this year and retails for 200 dollars with a 10 dollar a month subscription（订阅）fee.He said the company had received thousands of inquiries about the device since launching it this week. " Fifty percent are positive , 50 percent are negative , that it ' s a bit Big Brotherish（干涉人身自由的）," he said. _____________(50)________(50)A:"It will text you immediately."B:Double fixing devices easy to handle.C:Parents can also log on to the company website to discover their child's present location.D:"It uses GPS and GSM(Global System for Mobiles)technology with an accuracy of 10 feet(threemeters),"he said.E:"But it's really just about letting you have freedom of mind."F:"Even if the child managed to get it off it would send an emergency text message through to your mobile phone,"he said.
The smog is due（ ）invisible gases，mostly from automobile exhaust.A.from B.to C.for D.with
Examine the following command: CREATE TABLE (prod_id number(4), Prod_name varchar2 (20), Category_id number(30), Quantity_on_hand number (3) INVISIBLE); Which three statements are true about using an invisible column in the PRODUCTS table?（）A、The %ROWTYPE attribute declarations in PL/SQL to access a row will not display the invisible column in the output.B、The DESCRIBE commands in SQL *Plus will not display the invisible column in the output.C、Referential integrity constraint cannot be set on the invisible column.D、The invisible column cannot be made visible and can only be marked as unused.E、A primary key constraint can be added on the invisible column.
You have altered a non-unique index to be invisible to determine if queries execute within an acceptable response time without using this index. Which two are possible if table updates are performed which affect the invisible index columns?（）A、The index remains invisible.B、The index is not updated by the DML statements on the indexed table.C、The index automatically becomes visible in order to have it updated by DML on the table.D、The index becomes unusable but the table is updated by the DML.E、The index is updated by the DML on the table.
