diff --git a/core/ast/__init__.py b/core/ast/__init__.py
index 9d54b22..804646a 100644
--- a/core/ast/__init__.py
+++ b/core/ast/__init__.py
@@ -4,7 +4,7 @@
 This module provides the node types and classes for representing SQL query structures.
 """
 
-from .node_type import NodeType
+from .enums import NodeType
 from .node import (
     Node,
     TableNode,
@@ -18,6 +18,7 @@
     SelectNode,
     FromNode,
     WhereNode,
+    JoinNode,
     GroupByNode,
     HavingNode,
     OrderByNode,
@@ -40,9 +41,11 @@
     'SelectNode',
     'FromNode',
     'WhereNode',
+    'JoinNode',
     'GroupByNode',
     'HavingNode',
     'OrderByNode',
+    'OrderByItemNode',
     'LimitNode',
     'OffsetNode',
     'QueryNode'
diff --git a/core/ast/enums.py b/core/ast/enums.py
new file mode 100644
index 0000000..4a07d54
--- /dev/null
+++ b/core/ast/enums.py
@@ -0,0 +1,60 @@
+from enum import Enum
+
+# ============================================================================
+# Node Type Enumeration
+# ============================================================================
+
+class NodeType(Enum):
+    """Node type enumeration"""
+    
+    # Operands
+    TABLE = "table"
+    SUBQUERY = "subquery"
+    COLUMN = "column"
+    LITERAL = "literal"
+    # VarSQL specific
+    VAR = "var"
+    VARSET = "varset"
+
+    # Operators
+    OPERATOR = "operator"
+    FUNCTION = "function"
+    
+    # Query structure
+    SELECT = "select"
+    FROM = "from"
+    WHERE = "where"
+    JOIN = "join"
+    GROUP_BY = "group_by"
+    HAVING = "having"
+    ORDER_BY = "order_by"
+    ORDER_BY_ITEM = "order_by_item"
+    LIMIT = "limit"
+    OFFSET = "offset"
+    QUERY = "query"
+
+# ============================================================================
+# Join Type Enumeration
+# ============================================================================
+
+class JoinType(Enum):
+    """Join type enumeration"""
+    INNER = "inner"
+    OUTER = "outer"
+    LEFT = "left"
+    RIGHT = "right"
+    FULL = "full"
+    CROSS = "cross"
+    NATURAL = "natural"
+    SEMI = "semi"
+    ANTI = "anti"
+
+
+# ============================================================================
+# Sort Order Enumeration
+# ============================================================================
+
+class SortOrder(Enum):
+    """Sort order enum"""
+    ASC = "ASC"
+    DESC = "DESC"
\ No newline at end of file
diff --git a/core/ast/node.py b/core/ast/node.py
index d27584b..befe799 100644
--- a/core/ast/node.py
+++ b/core/ast/node.py
@@ -2,7 +2,7 @@
 from typing import List, Set, Optional
 from abc import ABC
 
-from .node_type import NodeType
+from .enums import NodeType, JoinType, SortOrder
 
 # ============================================================================
 # Base Node Structure
@@ -13,6 +13,31 @@ class Node(ABC):
     def __init__(self, type: NodeType, children: Optional[Set['Node']|List['Node']] = None):
         self.type = type
         self.children = children if children is not None else set()
+    
+    def __eq__(self, other):
+        if not isinstance(other, Node):
+            return False
+        if self.type != other.type:
+            return False
+        if len(self.children) != len(other.children):
+            return False
+        # Compare children
+        if isinstance(self.children, set) and isinstance(other.children, set):
+            return self.children == other.children
+        elif isinstance(self.children, list) and isinstance(other.children, list):
+            return self.children == other.children
+        else:
+            return False
+    
+    def __hash__(self):
+        # Make nodes hashable by using their type and a hash of their children
+        if isinstance(self.children, set):
+            # For sets, create a deterministic hash by sorting children by their string representation
+            children_hash = hash(tuple(sorted(self.children, key=lambda x: str(x))))
+        else:
+            # For lists, just hash the tuple directly
+            children_hash = hash(tuple(self.children))
+        return hash((self.type, children_hash))
 
 
 # ============================================================================
@@ -25,6 +50,16 @@ def __init__(self, _name: str, _alias: Optional[str] = None, **kwargs):
         super().__init__(NodeType.TABLE, **kwargs)
         self.name = _name
         self.alias = _alias
+    
+    def __eq__(self, other):
+        if not isinstance(other, TableNode):
+            return False
+        return (super().__eq__(other) and 
+                self.name == other.name and 
+                self.alias == other.alias)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.name, self.alias))
 
 
 # TODO - including query structure arguments (similar to QueryNode) in constructor.
@@ -43,6 +78,17 @@ def __init__(self, _name: str, _alias: Optional[str] = None, _parent_alias: Opti
         self.alias = _alias
         self.parent_alias = _parent_alias
         self.parent = _parent
+    
+    def __eq__(self, other):
+        if not isinstance(other, ColumnNode):
+            return False
+        return (super().__eq__(other) and 
+                self.name == other.name and 
+                self.alias == other.alias and 
+                self.parent_alias == other.parent_alias)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.name, self.alias, self.parent_alias))
 
 
 class LiteralNode(Node):
@@ -51,6 +97,15 @@ def __init__(self, _value: str|int|float|bool|datetime|None, **kwargs):
         super().__init__(NodeType.LITERAL, **kwargs)
         self.value = _value
 
+    def __eq__(self, other):
+        if not isinstance(other, LiteralNode):
+            return False
+        return (super().__eq__(other) and 
+                self.value == other.value)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.value))
+
 
 class VarNode(Node):
     """VarSQL variable node"""
@@ -72,16 +127,57 @@ def __init__(self, _left: Node, _name: str, _right: Optional[Node] = None, **kwa
         children = [_left, _right] if _right else [_left]
         super().__init__(NodeType.OPERATOR, children=children, **kwargs)
         self.name = _name
+    
+    def __eq__(self, other):
+        if not isinstance(other, OperatorNode):
+            return False
+        return (super().__eq__(other) and 
+                self.name == other.name)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.name))
 
 
 class FunctionNode(Node):
     """Function call node"""
-    def __init__(self, _name: str, _args: Optional[List[Node]] = None, **kwargs):
+    def __init__(self, _name: str, _args: Optional[List[Node]] = None, _alias: Optional[str] = None, **kwargs):
         if _args is None:
             _args = []
         super().__init__(NodeType.FUNCTION, children=_args, **kwargs)
         self.name = _name
-
+        self.alias = _alias
+    
+    def __eq__(self, other):
+        if not isinstance(other, FunctionNode):
+            return False
+        return (super().__eq__(other) and 
+                self.name == other.name and 
+                self.alias == other.alias)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.name, self.alias))
+
+
+class JoinNode(Node):
+    """JOIN clause node"""
+    def __init__(self, _left_table: 'TableNode', _right_table: 'TableNode', _join_type: JoinType = JoinType.INNER, _on_condition: Optional['Node'] = None, **kwargs):
+        children = [_left_table, _right_table]
+        if _on_condition:
+            children.append(_on_condition)
+        super().__init__(NodeType.JOIN, children=children, **kwargs)
+        self.left_table = _left_table
+        self.right_table = _right_table
+        self.join_type = _join_type
+        self.on_condition = _on_condition
+    
+    def __eq__(self, other):
+        if not isinstance(other, JoinNode):
+            return False
+        return (super().__eq__(other) and 
+                self.join_type == other.join_type)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.join_type))
 
 # ============================================================================
 # Query Structure Nodes
@@ -89,20 +185,20 @@ def __init__(self, _name: str, _args: Optional[List[Node]] = None, **kwargs):
 
 class SelectNode(Node):
     """SELECT clause node"""
-    def __init__(self, _items: Set['Node'], **kwargs):
+    def __init__(self, _items: List['Node'], **kwargs):
         super().__init__(NodeType.SELECT, children=_items, **kwargs)
 
 
 # TODO - confine the valid NodeTypes as children of FromNode
 class FromNode(Node):
     """FROM clause node"""
-    def __init__(self, _sources: Set['Node'], **kwargs):
+    def __init__(self, _sources: List['Node'], **kwargs):
         super().__init__(NodeType.FROM, children=_sources, **kwargs)
 
 
 class WhereNode(Node):
     """WHERE clause node"""
-    def __init__(self, _predicates: Set['Node'], **kwargs):
+    def __init__(self, _predicates: List['Node'], **kwargs):
         super().__init__(NodeType.WHERE, children=_predicates, **kwargs)
 
 
@@ -114,13 +210,28 @@ def __init__(self, _items: List['Node'], **kwargs):
 
 class HavingNode(Node):
     """HAVING clause node"""
-    def __init__(self, _predicates: Set['Node'], **kwargs):
+    def __init__(self, _predicates: List['Node'], **kwargs):
         super().__init__(NodeType.HAVING, children=_predicates, **kwargs)
 
 
+class OrderByItemNode(Node):
+    """Single ORDER BY item"""
+    def __init__(self, _column: Node, _sort: SortOrder = SortOrder.ASC, **kwargs):
+        super().__init__(NodeType.ORDER_BY_ITEM, children=[_column], **kwargs)
+        self.sort = _sort
+
+    def __eq__(self, other):
+        if not isinstance(other, OrderByItemNode):
+            return False
+        return (super().__eq__(other) and 
+                self.sort == other.sort)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.sort))
+
 class OrderByNode(Node):
     """ORDER BY clause node"""
-    def __init__(self, _items: List['Node'], **kwargs):
+    def __init__(self, _items: List[OrderByItemNode], **kwargs):
         super().__init__(NodeType.ORDER_BY, children=_items, **kwargs)
 
 
@@ -129,6 +240,15 @@ class LimitNode(Node):
     def __init__(self, _limit: int, **kwargs):
         super().__init__(NodeType.LIMIT, **kwargs)
         self.limit = _limit
+    
+    def __eq__(self, other):
+        if not isinstance(other, LimitNode):
+            return False
+        return (super().__eq__(other) and 
+                self.limit == other.limit)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.limit))
 
 
 class OffsetNode(Node):
@@ -136,6 +256,15 @@ class OffsetNode(Node):
     def __init__(self, _offset: int, **kwargs):
         super().__init__(NodeType.OFFSET, **kwargs)
         self.offset = _offset
+    
+    def __eq__(self, other):
+        if not isinstance(other, OffsetNode):
+            return False
+        return (super().__eq__(other) and 
+                self.offset == other.offset)
+    
+    def __hash__(self):
+        return hash((super().__hash__(), self.offset))
 
 
 class QueryNode(Node):
diff --git a/core/ast/node_type.py b/core/ast/node_type.py
deleted file mode 100644
index 2bae729..0000000
--- a/core/ast/node_type.py
+++ /dev/null
@@ -1,32 +0,0 @@
-from enum import Enum
-
-# ============================================================================
-# Node Type Enumeration
-# ============================================================================
-
-class NodeType(Enum):
-    """Node type enumeration"""
-    
-    # Operands
-    TABLE = "table"
-    SUBQUERY = "subquery"
-    COLUMN = "column"
-    LITERAL = "literal"
-    # VarSQL specific
-    VAR = "var"
-    VARSET = "varset"
-
-    # Operators
-    OPERATOR = "operator"
-    FUNCTION = "function"
-    
-    # Query structure
-    SELECT = "select"
-    FROM = "from"
-    WHERE = "where"
-    GROUP_BY = "group_by"
-    HAVING = "having"
-    ORDER_BY = "order_by"
-    LIMIT = "limit"
-    OFFSET = "offset"
-    QUERY = "query"
diff --git a/tests/test_query_parser.py b/tests/test_query_parser.py
index 8b176f9..c3e7b61 100644
--- a/tests/test_query_parser.py
+++ b/tests/test_query_parser.py
@@ -5,7 +5,7 @@
     LiteralNode, OperatorNode, FunctionNode, GroupByNode, HavingNode,
     OrderByNode, LimitNode, OffsetNode, SubqueryNode, VarNode, VarSetNode
 )
-from core.ast.node_type import NodeType
+from core.ast.enums import NodeType, JoinType, SortOrder
 from data.queries import get_query
 
 parser = QueryParser()