RA-Query - a tool for RA Query Execution

Instructions to create executable file : 1) Execte the following command in terminal : g++ -std=c++11 QProcessor.cpp -o RAQuery 2) Now execute the RAQuery executable so created.

This tool assumes input as space-seprated stream of tokens. So it is advised to seprate each token by atleast one space & Relation names / Attribute names / Attribute Values must be devoid of any spaces as well ( Use '_' for multi-word Relation names / Attribute names / Attribute Values ). This tool is Case-Sensitive. So it is advised to keep case in mind while executing queries. Operations available in this tool & their Syntax is as given below :

1. Project Operation : Purpose of this Operation is to carry out Projection of certain columns of a Relation. This operation can be carried out using 'P' operator provided with this tool. 'P' is a binary operator, which takes first argument as a Relation Name or a expression evaluating to Relation, & the second argument is a '|' (pipe) seprated list of attributes included in the Result, enclosed within parantheses.

   Syntax :
   	[ RelationA P (Attribute1|Attribute2|Attribute3|....|AttributeN) ]
   
   Notes Regarding this Operator :
   	Attribute list is required to be devoid of any spaces.
   	RelationA can be name of some pre-existing relation or an expression evaluating to a Relation.
   

2. Rename Operation : Purpose of this Operation is to Rename a Relation existing in Database or result of some expression which evaluates to a Relation. This operation can be carried out using 'R' operator provided with this tool. 'R' is a binary operator, which takes first argument as a Relation Name or a expression evaluating to Relation, & the second argument is a '|' (pipe) seprated list of newRelation name & newAttribute names, enclosed within parantheses. Second argument can be a single name, enclosed within parantheses, in this case attribute names of Relation are preserved, only Relation name is changed.

   Syntax :
   	[ RelationA R (newRelationA|newAttribute1|newAttribute2|newAttribute3|....|newAttributeN) ]
   		OR
   	[ RelationA R (newRelationA) ]       
   
   Notes Regarding this Operator :
   	new Name list is required to be devoid of any spaces.
   	RelationA can be name of some pre-existing relation or an expression evaluating to a Relation.		
   

3. Union Operation : Purpose of this Operation is to carry out union of two Relations. This operation can be carried out using 'U' operator provided with this tool. 'U' is a binary operator, which takes two argument each being a Relation Name or a expression evaluating to Relation. Two relations passed as arguments must have same arity & domain (Data Type) of corressponding attributes must match as well.

   Syntax :
   	[ RelationA U RelationB ]
   
   Notes Regarding this Operator :
   	RelationA & RelationB can be name of some pre-existing relation or an expression evaluating to a Relation.
   

4. Set Difference Operation : Purpose of this Operation is to carry out Set Differnce of two Relations. This operation can be carried out using '-' operator provided with this tool. '-' is a binary operator, which takes two argument each being a Relation Name or a expression evaluating to Relation. Two relations passed as arguments must have same arity & domain (Data Type) of corressponding attributes must match as well. Result is of this operator is a relation including all tuple including in first relation, not present in second relation.

   Syntax :
   	[ RelationA - RelationB ]
   
   Notes Regarding this Operator :
   	RelationA & RelationB can be name of some pre-existing relation or an expression evaluating to a Relation.				
   

5. Cartesian Product Operation : Purpose of this Operation is to carry out Cartesian Product of two Relations. This operation can be carried out using 'X' operator provided with this tool. 'X' is a binary operator, which takes two argument each being a Relation Name or a expression evaluating to Relation. Result is of this operator is a relation including each tuple included in first relation glued with every tuple in second relation.

   Syntax :
   	[ RelationA X RelationB ]
   
   Notes Regarding this Operator :
   	RelationA & RelationB can be name of some pre-existing relation or an expression evaluating to a Relation.
   	Attributes if common in RelationA & RelationB are automatically renamed.
   

6. Selection Operation : Purpose of this Operation is to carry out Selection of certain tuple of a Relation, based on if they satisfy the specified predicate or not. This operation can be carried out using 'S' operator provided with this tool. 'S' is a binary operator, which takes first argument as a Relation Name or a expression evaluating to Relation, & the second argument is a Predicate Expression enclosed within parantheses.

   Syntax :
   	[ RelationA S PredicateExpression ]
   
   Notes Regarding this Operator :
   	RelationA can be name of some pre-existing relation or an expression evaluating to a Relation.
   
   Syntax for Predicate Expression :
   	1. Relational operators available with this tool are : (greater than) >> / (less than) << / (greater than or equal to) >= / (less than or equal to) <= /  (not equal to) <> / (equal to) == .
   	2. Logical operators available with this tool are : & (logical and) / | (logical or) / ! (logical not) 
   	3. Each constant if used is required to be appended with "@C".
   	4. Syntax for Predicate Expression can be defined as recursively as follows :
   		i. (Attribute1 RelOp Attribute2) & (Attribute1 RelOp Const) & (Const RelOp Attribute2) are Basic Predicate expression. (Spaces are included for undestanding purpose only, must be devoid of 		spaces)
   		ii. Any predicate expression formed using combination of two / one predicate expression is in itself a valid predicate expression.
   			((PredicateExpression1)&(PredicateExpression2)) and ((PredicateExpression1)|(PredicateExpression2)) and (!(PredicateExpression1))) are valid Predicate Expressions.
   

7. Natural Join Operation : Purpose of this Operation is to carry out Natural Join of two Relations. This operation can be carried out using 'J' operator provided with this tool. 'J' is a binary operator, which takes two argument each being a Relation Name or a expression evaluating to Relation. Result is of this operator is a relation including each tuple included in first relation glued with every tuple in second relation, provided the tuples to glued have same Attributes Values for Attributes common in two Relations ( Common Attributes are kept only once in resulting tuple).

   Syntax :
   	[ RelationA J RelationB ]
   
   Notes Regarding this Operator :
   	RelationA & RelationB can be name of some pre-existing relation or an expression evaluating to a Relation.
   	Attributes if common in RelationA & RelationB occur only once in the resulting relation.				
   

Some Operators provided to ease Table creation are as follows :

1. Create Table Operation : Purpose of this Operation is to create a empty Relation. This operation can be carried out using '*C' operator provided with this tool.

   Syntax :
   	*C [ RelationName ] [ Attribute1Name Attribute1DataType ] [ Attribute2Name Attribute2DataType ] [ Attribute3Name Attribute3DataType ] .... [ AttributeNName AttributeNDataType ];
   
   Notes Regarding this Operator :
   	Attribute Name / Relation Name is required to be devoid of any spaces.
   	RelationA must not be a pre-existing Relation.
   

2. Insert into Table Operation : Purpose of this Operation is to insert a tuple in pre-existing Relation. This operation can be carried out using '*I' operator provided with this tool.

   Syntax :
   	*I [ RelationA ] [ Attribute1Value Attribute2Value Attribute3Value ... AttributeNValue ];
   
   Notes Regarding this Operator :
   	Attribute Name / Relation Name is required to be devoid of any spaces.
   	RelationA must not be a pre-existing Relation.	
   

3. Save Table Operation : Purpose of this Operation is save a pre-existing Relation (in Temporary Database) into Permanent Database. This operation can be carried out using '*S' operator provided with this tool.

   Syntax :
   	*S [ RelationA ];
   
   Notes Regarding this Operator :
   	RelationA can be name of some pre-existing relation or an expression evaluating to a Relation.	
   

4. Exit Operation : Purpose of this Operation is to exit the Tool. This operation can be carried out using '*E' operator provided with this tool.

   Syntax :
   	*E;
   
   Notes Regarding this Operator :
   	Exiting using this operator allows you to save the relation in permanent database in "File.dat" file, from where they can be reloaded.
   

5. Show Tables Operation : Purpose of this Operation is to Show Tables in Permanent Database. This operation can be carried out using '*V' operator provided with this tool.

   Syntax :
   	*V;
   

Nested Queries have been implemented by firstly carrying out Postfix expression for given RA expresion & then evaluating the Postfix expression.