= SQL

http://github.com/omghax/sql

== DESCRIPTION:

Ruby library for parsing and generating SQL statements.

== FEATURES/PROBLEMS:

• Parse arbitrary SQL strings into an AST (abstract syntax tree), which can then be traversed.

• Allows your code to understand and manipulate SQL in a deeper way than just using string manipulation.

== SYNOPSIS:

Here's an example of manually building an AST. It's extremely verbose at the moment, but that should be mitigated a bit when I come up with a DSL for building these trees.

require 'rubygems' require 'sql'

Let's build a tree representing the SQL statement

"SELECT * FROM users WHERE id = 1"

We'll start from the rightmost side, and work our way left as we go.

First, the integer constant, "1"

integer_constant = SQL::Statement::Integer.new(1) integer_constant.to_sql => "1"

Now the column reference, "id"

column_reference = SQL::Statement::Column.new('id') column_reference.to_sql => "id"

Now we'll combine the two using an equals operator, to create a search

condition

search_condition = SQL::Statement::Equals.new(column_reference, integer_constant) search_condition.to_sql => "id = 1"

Next we'll feed that search condition to a where clause

where_clause = SQL::Statement::WhereClause.new(search_condition) where_clause.to_sql => "WHERE id = 1"

Next up is the FROM clause. First we'll build a table reference

users = SQL::Statement::Table.new('users') users.to_sql => "users"

Now we'll feed that table reference to a from clause

from_clause = SQL::Statement::FromClause.new(users) from_clause.to_sql => "FROM users"

Now to combine the FROM and WHERE clauses to form a table expression

table_expression = SQL::Statement::TableExpression.new(from_clause, where_clause) table_expression.to_sql => "FROM users WHERE id = 1"

Now we need to represent the asterisk "*"

all = SQL::Statement::All.new all.to_sql => "*"

Now we're ready to hand off these objects to a select statement

select_statement = SQL::Statement::Select.new(all, table_expression) select_statement.to_sql => "SELECT * FROM users WHERE id = 1"

== ROADMAP

These features aren't currently implemented, but I have plans to add them in the future. Stay tuned.

Eventually I plan to implement a SQL parser that will generate the tree structure for you, based on an input string of SQL.

require 'rubygems' require 'sql' parser = SQL::Parser.new

Build the AST from a SQL statement

ast = parser.scan_str('SELECT * FROM users WHERE id = 1')

Find which columns where selected in the FROM clause

ast.select_list.to_sql => "*"

Output the table expression as SQL

ast.table_expression.to_sql => "FROM users WHERE id = 1"

Drill down into the WHERE clause, to examine every piece

ast.table_expression.where_clause.to_sql => "WHERE id = 1" ast.table_expression.where_clause.search_condition.to_sql => "id = 1" ast.table_expression.where_clause.search_condition.left.to_sql => "id" ast.table_expression.where_clause.search_condition.right.to_sql => "1"

== REQUIREMENTS:

• Ruby (duh)
• RubyGems
• Hoe >= 1.6.0

== INSTALL:

$ sudo gem install omghax-sql --source http://gems.github.com

== LICENSE:

(The MIT License)

Copyright (c) 2008 Dray Lacy

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.