Added support for MySQL type backticks quoting for identifiers for both parsing and SQL generation.

Usage:
SQLTree.identifier_quote_char = '`'

Author: wvanbergen

lib/sql_tree.rb

@@ -5,6 +5,14 @@
 # necessary files for the gem to function properly.
 module SQLTree
 
+  class << self
+    # The character to quote variable names with.
+    attr_accessor :identifier_quote_char
+  end
+  
+  # Set default quote characters
+  self.identifier_quote_char = '"'
+    
   # Loads constants in the SQLTree namespace using self.load_default_class_file(base, const)
   # <tt>const</tt>:: The constant that is not yet loaded in the SQLTree namespace. This should be passed as a string or symbol.
   def self.const_missing(const)

lib/sql_tree/node.rb

@@ -27,13 +27,13 @@ def inspect
     # SQL queries.
     # <tt>name</tt>:: The name of the variable to quote.
     def quote_var(name)
-      "\"#{name}\"" # TODO: MySQL style variable quoting
+      "#{SQLTree.identifier_quote_char}#{name}#{SQLTree.identifier_quote_char}" # TODO: MySQL style variable quoting
     end
 
     # Quotes a string so that it can be used safey within an SQL query.
     # <tt>str</tt>:: The string to quote.
     def quote_str(str)
-      "'#{str.gsub(/\'/, "''")}'"
+      "'#{str.gsub("'", "''")}'"
     end
 
     # Parses an SQL fragment tree from a stream of tokens.

lib/sql_tree/tokenizer.rb

@@ -84,6 +84,7 @@ def empty_keyword_queue!(&block) # :yields: SQLTree::Token
   # This method is aliased to <tt>:each</tt> to make the Enumerable
   # methods work on this method.
   def each_token(&block) # :yields: SQLTree::Token
+    
     while next_char
       case current_char
       when /^\s?$/;        # whitespace, go to next character
@@ -93,9 +94,9 @@ def each_token(&block) # :yields: SQLTree::Token
       when ',';            handle_token(SQLTree::Token::COMMA, &block)
       when /\d/;           tokenize_number(&block)
       when "'";            tokenize_quoted_string(&block)
-      when OPERATOR_CHARS; tokenize_operator(&block)
       when /\w/;           tokenize_keyword(&block)
-      when '"';            tokenize_quoted_variable(&block)     # TODO: allow MySQL quoting mode
+      when OPERATOR_CHARS; tokenize_operator(&block)
+      when SQLTree.identifier_quote_char; tokenize_quoted_identifier(&block)
       end
     end
 
@@ -154,9 +155,9 @@ def tokenize_quoted_string(&block) # :yields: SQLTree::Token::String
   #
   # The actual quote character that is used depends on the DBMS. For now,
   # only the more standard double quote is accepted.
-  def tokenize_quoted_variable(&block) # :yields: SQLTree::Token::Identifier
+  def tokenize_quoted_identifier(&block) # :yields: SQLTree::Token::Identifier
     variable = ''
-    until next_char.nil? || current_char == '"' # TODO: allow MySQL quoting mode
+    until next_char.nil? || current_char == SQLTree.identifier_quote_char # TODO: allow MySQL quoting mode
       variable << (current_char == "\\" ? next_char : current_char)
     end
     handle_token(SQLTree::Token::Identifier.new(variable), &block)

spec/integration/parse_and_generate_spec.rb

@@ -2,9 +2,17 @@
 
 describe SQLTree, 'parsing and generating SQL' do
 
+  before(:each) { SQLTree.identifier_quote_char = '"' }
+
   it "should parse an generate q query without FROM" do
     SQLTree['SELECT 1'].to_sql.should == 'SELECT 1'
   end
+  
+  it "should parse and generate MySQL type identifier quotes" do
+    SQLTree.identifier_quote_char = "`"
+    SQLTree['SELECT `field` FROM `table`'].to_sql.should == 
+            'SELECT `field` FROM `table`'
+  end
 
   it "should parse and generate SQL fo a simple list query" do
     SQLTree["SELECT * FROM table"].to_sql.should == 'SELECT * FROM "table"'