sql parser

A simple parser for sql made using lex yacc / GNU's flex bison.

It currently supports only selected sql queries as stated below.

How to make

• go to source folder cd src
• make to build : this will generate the usual files and executes the executable file

Assumptions

• queries are case-insensitive
• each query ends with semicolon
• keywords cant be identifiers

Syntax

UPDATE table_reference SET assignment_list [WHERE where_condition] [ORDER BY ...] [LIMIT row_count]

Cases Handled

• update table_reference set assignment_list

  update customer set bonus = 1000;
  update customer set bonus = 1000, gst = 200;
  update customer set bonus = 1000, gst = 200, bonus_type = 'Diwali';
  update customer set bonus = 1000, gst = 200, bonus_type = 'Diwali', extra = bonus + 200;
  update customer set bonus = 1000, gst = 2 * 10 ;
  update customer set bonus = 1000, gst = 2 * 5 + 5 - 10 / 2;
  

• update table_reference set assignment_list where condition_list

  update customer set bonus = 1000, gst = 20 where bonus_type = 'Diwali';
  update customer set bonus = 1000, gst = 20 where bonus_type = 'Diwali' and salary >= 40000;
  update customer set bonus = 1000, gst = 20 where bonus_type = 'Diwali' and salary >= 40000 or salary <= 20000;
  update customer set bonus = 1000, gst = 20 where bonus_type = 'Diwali' and salary between 40000 and 20000;
  

• update table_reference set assignment_list order by column

  update customer set bonus = 1000, gst = 20 order by cid;
  update customer set bonus = 1000, gst = 20 order by cid asc, salary desc;
  

• update table_reference set assignment_list Limit row_count

  update customer set bonus = 1000, gst = 20 limit 10;
  

• update table_reference set assignment_list where condition_list order by column Limit row_count

  update customer set bonus = 1000, gst = 20 where bonus_type = 'Diwali' and salary >= 40000 or salary <= 20000 order by cid desc limit 5;
  

Cases Not Handled

• multi-table updates

  update items,month set items.price=month.price where items.id = month.id;
  

• Binary operator such as XOR, NOT, |(or), &(and)

Reference links

• Lex Yacc Introduction

  • https://silcnitc.github.io/lex.html
  • https://silcnitc.github.io/yacc.html
  • https://silcnitc.github.io/ywl.html
  • http://epaperpress.com/lexandyacc/intro.html
  • http://dinosaur.compilertools.net/lex/
  • http://dinosaur.compilertools.net/yacc/

• Lex yacc primer

  • http://tldp.org/HOWTO/Lex-YACC-HOWTO-7.html

• Bison manual references

  • http://www.gnu.org/software/bison/manual/html_node/Understanding.html
  • http://www.gnu.org/software/bison/manual/bison.html#Action-Features
  • http://www.gnu.org/software/bison/manual/bison.html#Algorithm
  • http://www.gnu.org/software/bison/manual/html_node/Error-Recovery.html