RAM_SQL

A ground up, RAM based implementation of SQL using C++

Instructions

To compile and generate executable file, type 'make' (without quotes)

An executable file named 'dbms' will be generated

Type ./dbms to run it

Type your SQL queries after the ">>" prompt and suffix it with ';'

To use an input file, use "./dbms < input_file_name". Make sure to give "exit;" command in the end to avoid infinite loop

A sample input file named input.txt has been provided. Type ./dbms < input.txt to run it.

To delete the generated executable file and log file, type 'make clean'

Things you can do with this RAM Based DBMS:

Create table (with checks for default, not null etc)

Insert command (either insert in all columns or selected columns (not inserting in column without default will raise ERROR))

select command, with conditions after where clause

In, not in

Nested queries (nested two levels)

drop table

Aliases: can provide alias of any length to any column (not just single letter)

delete tuples from a table in database

Queries can be given in any case. They're case insensitive, like SQL queries.

Multiple spaces or newlines can be given between tokens in a query. The parser will handle it.

..........And much more

Control Flow of a few example queries:

create table students(Name varchar(20) not null,Roll int not null,Age int default 20);

Remove white spaces and insert it into tokens vector

create function is invoked because tokens[0]="create"

Write info to log file, with timestamp

Table with same name doesn't exist, so enter table name into tables vector

Set Name as varchar(20) not null

Set Roll as int not null

Set Age as int default = 20

drop table students

Remove white spaces and insert it into tokens vector

drop function is invoked because tokens[0]="drop"

Write info to log file, with timestamp

Remove entry from table, db, and col vectors

INSERT into students(Name,Roll) values("Ayush",5);

Remove white spaces and insert it into tokens vector

insert function is invoked because tokens[0]="insert"

Write info to log file, with timestamp

Enter "Ayush" in Name

Enter 5 in Roll

Age value is not specified, but it has default value 20, so 20 is inserted

SELECT * from students WHERE name in ( "Atharva", "Pratik");

Remove white spaces and insert into token vector

select function is invoked because tokens[0]="select"

Write info to log file, with timestamp

find name of table and check in database

check for where keyword and invokes it

In where it goes to else condition

here it finds "in" keyword and then create vector temp

since there is no nested select statement, it will go to else part again.

push in result the corresponding row_ids which satisfy condition and return result

come back to select function, since it is * it will push all cols and return result

now print is called with result as argument

it will print all the corresponding rows and columns

DELETE from students where name="Pranav" or Roll>10;

Remove white spaces and insert into token vector

delete function is invoked because tokens[0]="delete"

Write info to log file, with timestamp

find name of table and check in database

check for where keyword and invokes it

In where it goes to else condition

calls RELOP function

then check "or" keyword and implement it

return array of rowids needs to be deleted

come back to delete function

now delete corresponding rows