/ra_console

Implementation of Relational Algebra functions

Primary LanguageC++

Implementation of Relational Algebra functions

Aim of the Project

To write a program in C++ to implement Relational Algebra functions present in DBMS.

Functions implemented

The program implements the following Relational Algebra functions:

  1. SELECT

  2. PROJECT

  3. RENAME

  4. UNION

  5. SET DIFFERENCE

  6. CARTESIAN PRODUCT

Project Details

The program assumes the following:

  • The database folder is present in the same directory as the main project file
  • The database folder has a db_info.txt file containing the details of the database
  • The database folder has a tables subdirectory which contains all table files in space separated form in .txt format
  • The tables have their schema in the top three lines:
    • First line has table name
    • Second line has column names
    • Third line has column data types
  • The data in the files is valid:
    • There is no newline
    • All data has same number of columns (except) table name
    • The data types corresponding to the data are correct
  • The data types allowed are:
    • int
    • float
    • varchar
  • Comparison accross data types is not allowed
  • Queries are delimited by a ;

Syntax

The basic syntax of the queries is as follows:

Show tables in database as specified in db_info.txt:

SHOW_TABLES;

SELECT:

SEL{predicate}(table_name);

PROJECT:

PRO{column_name1:column_name2}(table_name);

RENAME:

REN{new_table_name|column_name1:column_name2}(table_name);

UNION:

UNI(table_name1, table_name2);

SET DIFFERENCE:

DIF(table_name1, table_name2);

CARTESIAN PRODUCT:

CRP(table_name1, table_name2);

EXIT:

EXIT;

The predicate syntax for SEL:

SEL{(a > b | c = d) & e ! f}(table_name);

The available operators are:

  1. + : Add two ints or floats
  2. - : Subtract two ints or floats
  3. * : Multiply two ints or floats
  4. / : Divide two ints or floats
  5. = : Compare two operands, TRUE if equal
  6. ! : Compare two operands, TRUE if unequal
  7. > : Compare two operands, TRUE if former is greater than latter
  8. < : Compare two operands, TRUE if former is lesser than latter
  9. & : Logical AND
  10. | : Logical OR

NOTES:

  • Comparison between different data types is not allowed

  • varchar (Strings) are enclosed in '

  • float operands must have a .

  • Invalid operands are not allowed

The predicate syntax for PRO:

PRO{a:b:c:d}(table_name);

NOTES:

  • Column names must be separated by a :

  • Column names must be present in table

  • Column names are displayed in given order

The predicate syntax for REN:

REN{new_table_name|a:b:c:d}(table_name);
REN{new_table_name}(table_name);

NOTES:

  • Table name and column names must be separated by a |

  • Column names must be separated by a :

  • Column names must be valid

  • Column names are renamed in given order

  • If no column names are provided, the colum names are retained

  • Either all or none of the column names must be provided

Sample Queries

1. SEL{faculty.salary > 80000 & dept = 'CSE'}(faculty);
2. PRO{id:name:grade}(studuent);
3. UNI(PRO{name}(faculty), PRO{name}(student));
4. DIF(PRO{name}(faculty), PRO{name}(student));
5. CRP(student, course);
6. REN{stud|stud_id:name:cgpa}(student);

For more queries, see Query file

Comments:

  • Syntax errors are not allowed
  • SELECT takes exactly one predicate
  • RENAME cannot rename to a table already present
  • Column and table names must be alphanumeric
  • Invalid comparisons between data types are not allowed
  • UNI and DIF operations must have same column names and data types. Order need not be same
  • Nested queries are allowed
  • CRP operation needs different column names
  • PRO should have unique column names
  • All whitespaces are ignored