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UGC NET CSE | June 2013 | Part 3 | Question: 7

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The “PROJECT” operator of a relational algebra creates a new table that has always

  1. More columns than columns in original table
  2. More rows than original table
  3. Same number of rows as the original table
  4. Same number of columns as the original table
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Ans C

The “PROJECT” operator of a relational algebra gives only specified column values.

 R1              
  Name    Room    
  ============   
  coke     633   
  bass     633   
  bashful  633    
  tab      628   
  crush    628

if R2 = PROJECT(Room)

 R2              
      Room    
  =======   
      633   
      633   
      633    
      628   
      628

a) Number of columns will be less that or equal to original table. A is false.

b) No row will be added while separating a column. B is also false.

c) PROJCT opeartion will keep duplicate row values. C is true.

d) PROJECT operation will remove some columns if all column names are not specified in it. You can see in given example, name column is removed. Hence d is also false.

~~Correct me if i am wrong!~

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