diff --git a/src/ast/ddl.rs b/src/ast/ddl.rs
index d48400b1..78ec2e0c 100644
--- a/src/ast/ddl.rs
+++ b/src/ast/ddl.rs
@@ -67,6 +67,15 @@ pub enum AlterTableOperation {
         data_type: DataType,
         options: Vec<ColumnOption>,
     },
+    /// `RENAME CONSTRAINT <old_constraint_name> TO <new_constraint_name>`
+    ///
+    /// Note: this is a PostgreSQL-specific operation.
+    RenameConstraint { old_name: Ident, new_name: Ident },
+    /// `ALTER [ COLUMN ]`
+    AlterColumn {
+        column_name: Ident,
+        op: AlterColumnOperation,
+    },
 }
 
 impl fmt::Display for AlterTableOperation {
@@ -85,6 +94,9 @@ impl fmt::Display for AlterTableOperation {
             AlterTableOperation::AddColumn { column_def } => {
                 write!(f, "ADD COLUMN {}", column_def.to_string())
             }
+            AlterTableOperation::AlterColumn { column_name, op } => {
+                write!(f, "ALTER COLUMN {} {}", column_name, op)
+            }
             AlterTableOperation::DropPartitions {
                 partitions,
                 if_exists,
@@ -139,6 +151,51 @@ impl fmt::Display for AlterTableOperation {
                     write!(f, " {}", display_separated(options, " "))
                 }
             }
+            AlterTableOperation::RenameConstraint { old_name, new_name } => {
+                write!(f, "RENAME CONSTRAINT {} TO {}", old_name, new_name)
+            }
+        }
+    }
+}
+
+/// An `ALTER COLUMN` (`Statement::AlterTable`) operation
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum AlterColumnOperation {
+    /// `SET NOT NULL`
+    SetNotNull,
+    /// `DROP NOT NULL`
+    DropNotNull,
+    /// `SET DEFAULT <expr>`
+    SetDefault { value: Expr },
+    /// `DROP DEFAULT`
+    DropDefault,
+    /// `[SET DATA] TYPE <data_type> [USING <expr>]`
+    SetDataType {
+        data_type: DataType,
+        /// PostgreSQL specific
+        using: Option<Expr>,
+    },
+}
+
+impl fmt::Display for AlterColumnOperation {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            AlterColumnOperation::SetNotNull => write!(f, "SET NOT NULL",),
+            AlterColumnOperation::DropNotNull => write!(f, "DROP NOT NULL",),
+            AlterColumnOperation::SetDefault { value } => {
+                write!(f, "SET DEFAULT {}", value)
+            }
+            AlterColumnOperation::DropDefault {} => {
+                write!(f, "DROP DEFAULT")
+            }
+            AlterColumnOperation::SetDataType { data_type, using } => {
+                if let Some(expr) = using {
+                    write!(f, "SET DATA TYPE {} USING {}", data_type, expr)
+                } else {
+                    write!(f, "SET DATA TYPE {}", data_type)
+                }
+            }
         }
     }
 }
diff --git a/src/ast/mod.rs b/src/ast/mod.rs
index e7b8e7a0..a1a4453b 100644
--- a/src/ast/mod.rs
+++ b/src/ast/mod.rs
@@ -31,8 +31,8 @@ use serde::{Deserialize, Serialize};
 
 pub use self::data_type::DataType;
 pub use self::ddl::{
-    AlterTableOperation, ColumnDef, ColumnOption, ColumnOptionDef, ReferentialAction,
-    TableConstraint,
+    AlterColumnOperation, AlterTableOperation, ColumnDef, ColumnOption, ColumnOptionDef,
+    ReferentialAction, TableConstraint,
 };
 pub use self::operator::{BinaryOperator, UnaryOperator};
 pub use self::query::{
@@ -592,6 +592,22 @@ impl fmt::Display for ShowCreateObject {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum CommentObject {
+    Column,
+    Table,
+}
+
+impl fmt::Display for CommentObject {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            CommentObject::Column => f.write_str("COLUMN"),
+            CommentObject::Table => f.write_str("TABLE"),
+        }
+    }
+}
+
 /// A top-level statement (SELECT, INSERT, CREATE, etc.)
 #[allow(clippy::large_enum_variant)]
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -779,6 +795,14 @@ pub enum Statement {
         snapshot: Option<Value>,
         session: bool,
     },
+    /// `COMMENT ON ...`
+    ///
+    /// Note: this is a PostgreSQL-specific statement.
+    Comment {
+        object_type: CommentObject,
+        object_name: ObjectName,
+        comment: Option<String>,
+    },
     /// `COMMIT [ TRANSACTION | WORK ] [ AND [ NO ] CHAIN ]`
     Commit { chain: bool },
     /// `ROLLBACK [ TRANSACTION | WORK ] [ AND [ NO ] CHAIN ]`
@@ -1459,6 +1483,18 @@ impl fmt::Display for Statement {
                 }
                 write!(f, "AS {}", statement)
             }
+            Statement::Comment {
+                object_type,
+                object_name,
+                comment,
+            } => {
+                write!(f, "COMMENT ON {} {} IS ", object_type, object_name)?;
+                if let Some(c) = comment {
+                    write!(f, "'{}'", c)
+                } else {
+                    write!(f, "NULL")
+                }
+            }
         }
     }
 }
diff --git a/src/keywords.rs b/src/keywords.rs
index 0695395c..56f77cc2 100644
--- a/src/keywords.rs
+++ b/src/keywords.rs
@@ -128,6 +128,7 @@ define_keywords!(
     COLLECT,
     COLUMN,
     COLUMNS,
+    COMMENT,
     COMMIT,
     COMMITTED,
     COMPUTE,
@@ -161,6 +162,7 @@ define_keywords!(
     CURRENT_USER,
     CURSOR,
     CYCLE,
+    DATA,
     DATABASE,
     DATE,
     DAY,
@@ -469,6 +471,7 @@ define_keywords!(
     TRUE,
     TRUNCATE,
     TRY_CAST,
+    TYPE,
     UESCAPE,
     UNBOUNDED,
     UNCOMMITTED,
diff --git a/src/parser.rs b/src/parser.rs
index b01c6090..a90db514 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -191,6 +191,9 @@ impl<'a> Parser<'a> {
                     self.prev_token();
                     Ok(self.parse_insert()?)
                 }
+                Keyword::COMMENT if dialect_of!(self is PostgreSqlDialect) => {
+                    Ok(self.parse_comment()?)
+                }
                 _ => self.expected("an SQL statement", Token::Word(w)),
             },
             Token::LParen => {
@@ -1944,7 +1947,12 @@ impl<'a> Parser<'a> {
                 }
             }
         } else if self.parse_keyword(Keyword::RENAME) {
-            if self.parse_keyword(Keyword::TO) {
+            if dialect_of!(self is PostgreSqlDialect) && self.parse_keyword(Keyword::CONSTRAINT) {
+                let old_name = self.parse_identifier()?;
+                self.expect_keyword(Keyword::TO)?;
+                let new_name = self.parse_identifier()?;
+                AlterTableOperation::RenameConstraint { old_name, new_name }
+            } else if self.parse_keyword(Keyword::TO) {
                 let table_name = self.parse_object_name()?;
                 AlterTableOperation::RenameTable { table_name }
             } else {
@@ -2014,6 +2022,38 @@ impl<'a> Parser<'a> {
                 data_type,
                 options,
             }
+        } else if self.parse_keyword(Keyword::ALTER) {
+            let _ = self.parse_keyword(Keyword::COLUMN);
+            let column_name = self.parse_identifier()?;
+            let is_postgresql = dialect_of!(self is PostgreSqlDialect);
+
+            let op = if self.parse_keywords(&[Keyword::SET, Keyword::NOT, Keyword::NULL]) {
+                AlterColumnOperation::SetNotNull {}
+            } else if self.parse_keywords(&[Keyword::DROP, Keyword::NOT, Keyword::NULL]) {
+                AlterColumnOperation::DropNotNull {}
+            } else if self.parse_keywords(&[Keyword::SET, Keyword::DEFAULT]) {
+                AlterColumnOperation::SetDefault {
+                    value: self.parse_expr()?,
+                }
+            } else if self.parse_keywords(&[Keyword::DROP, Keyword::DEFAULT]) {
+                AlterColumnOperation::DropDefault {}
+            } else if self.parse_keywords(&[Keyword::SET, Keyword::DATA, Keyword::TYPE])
+                || (is_postgresql && self.parse_keyword(Keyword::TYPE))
+            {
+                let data_type = self.parse_data_type()?;
+                let using = if is_postgresql && self.parse_keyword(Keyword::USING) {
+                    Some(self.parse_expr()?)
+                } else {
+                    None
+                };
+                AlterColumnOperation::SetDataType { data_type, using }
+            } else {
+                return self.expected(
+                    "SET/DROP NOT NULL, SET DEFAULT, SET DATA TYPE after ALTER COLUMN",
+                    self.peek_token(),
+                );
+            };
+            AlterTableOperation::AlterColumn { column_name, op }
         } else {
             return self.expected(
                 "ADD, RENAME, PARTITION or DROP after ALTER TABLE",
@@ -3547,6 +3587,35 @@ impl<'a> Parser<'a> {
             statement,
         })
     }
+
+    fn parse_comment(&mut self) -> Result<Statement, ParserError> {
+        self.expect_keyword(Keyword::ON)?;
+        let token = self.next_token();
+
+        let (object_type, object_name) = match token {
+            Token::Word(w) if w.keyword == Keyword::COLUMN => {
+                let object_name = self.parse_object_name()?;
+                (CommentObject::Column, object_name)
+            }
+            Token::Word(w) if w.keyword == Keyword::TABLE => {
+                let object_name = self.parse_object_name()?;
+                (CommentObject::Table, object_name)
+            }
+            _ => self.expected("comment object_type", token)?,
+        };
+
+        self.expect_keyword(Keyword::IS)?;
+        let comment = if self.parse_keyword(Keyword::NULL) {
+            None
+        } else {
+            Some(self.parse_literal_string()?)
+        };
+        Ok(Statement::Comment {
+            object_type,
+            object_name,
+            comment,
+        })
+    }
 }
 
 impl Word {
diff --git a/tests/sqlparser_common.rs b/tests/sqlparser_common.rs
index 4cbcd8e0..07a0db52 100644
--- a/tests/sqlparser_common.rs
+++ b/tests/sqlparser_common.rs
@@ -1950,6 +1950,108 @@ fn parse_alter_table_drop_column() {
     }
 }
 
+#[test]
+fn parse_alter_table_alter_column() {
+    let alter_stmt = "ALTER TABLE tab";
+    match verified_stmt(&format!(
+        "{} ALTER COLUMN is_active SET NOT NULL",
+        alter_stmt
+    )) {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::AlterColumn { column_name, op },
+        } => {
+            assert_eq!("tab", name.to_string());
+            assert_eq!("is_active", column_name.to_string());
+            assert_eq!(op, AlterColumnOperation::SetNotNull {});
+        }
+        _ => unreachable!(),
+    }
+
+    one_statement_parses_to(
+        "ALTER TABLE tab ALTER is_active DROP NOT NULL",
+        "ALTER TABLE tab ALTER COLUMN is_active DROP NOT NULL",
+    );
+
+    match verified_stmt(&format!(
+        "{} ALTER COLUMN is_active SET DEFAULT false",
+        alter_stmt
+    )) {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::AlterColumn { column_name, op },
+        } => {
+            assert_eq!("tab", name.to_string());
+            assert_eq!("is_active", column_name.to_string());
+            assert_eq!(
+                op,
+                AlterColumnOperation::SetDefault {
+                    value: Expr::Value(Value::Boolean(false))
+                }
+            );
+        }
+        _ => unreachable!(),
+    }
+
+    match verified_stmt(&format!(
+        "{} ALTER COLUMN is_active DROP DEFAULT",
+        alter_stmt
+    )) {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::AlterColumn { column_name, op },
+        } => {
+            assert_eq!("tab", name.to_string());
+            assert_eq!("is_active", column_name.to_string());
+            assert_eq!(op, AlterColumnOperation::DropDefault {});
+        }
+        _ => unreachable!(),
+    }
+}
+
+#[test]
+fn parse_alter_table_alter_column_type() {
+    let alter_stmt = "ALTER TABLE tab";
+    match verified_stmt("ALTER TABLE tab ALTER COLUMN is_active SET DATA TYPE TEXT") {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::AlterColumn { column_name, op },
+        } => {
+            assert_eq!("tab", name.to_string());
+            assert_eq!("is_active", column_name.to_string());
+            assert_eq!(
+                op,
+                AlterColumnOperation::SetDataType {
+                    data_type: DataType::Text,
+                    using: None,
+                }
+            );
+        }
+        _ => unreachable!(),
+    }
+
+    let res = Parser::parse_sql(
+        &GenericDialect {},
+        &format!("{} ALTER COLUMN is_active TYPE TEXT", alter_stmt),
+    );
+    assert_eq!(
+        ParserError::ParserError("Expected SET/DROP NOT NULL, SET DEFAULT, SET DATA TYPE after ALTER COLUMN, found: TYPE".to_string()),
+        res.unwrap_err()
+    );
+
+    let res = Parser::parse_sql(
+        &GenericDialect {},
+        &format!(
+            "{} ALTER COLUMN is_active SET DATA TYPE TEXT USING 'text'",
+            alter_stmt
+        ),
+    );
+    assert_eq!(
+        ParserError::ParserError("Expected end of statement, found: USING".to_string()),
+        res.unwrap_err()
+    );
+}
+
 #[test]
 fn parse_bad_constraint() {
     let res = parse_sql_statements("ALTER TABLE tab ADD");
diff --git a/tests/sqlparser_postgres.rs b/tests/sqlparser_postgres.rs
index 941f9c5d..bff21da2 100644
--- a/tests/sqlparser_postgres.rs
+++ b/tests/sqlparser_postgres.rs
@@ -263,6 +263,50 @@ fn parse_create_table_constraints_only() {
     };
 }
 
+#[test]
+fn parse_alter_table_constraints_rename() {
+    match pg().verified_stmt("ALTER TABLE tab RENAME CONSTRAINT old_name TO new_name") {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::RenameConstraint { old_name, new_name },
+        } => {
+            assert_eq!("tab", name.to_string());
+            assert_eq!(old_name.to_string(), "old_name");
+            assert_eq!(new_name.to_string(), "new_name");
+        }
+        _ => unreachable!(),
+    }
+}
+
+#[test]
+fn parse_alter_table_alter_column() {
+    pg().one_statement_parses_to(
+        "ALTER TABLE tab ALTER COLUMN is_active TYPE TEXT USING 'text'",
+        "ALTER TABLE tab ALTER COLUMN is_active SET DATA TYPE TEXT USING 'text'",
+    );
+
+    match pg()
+        .verified_stmt("ALTER TABLE tab ALTER COLUMN is_active SET DATA TYPE TEXT USING 'text'")
+    {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::AlterColumn { column_name, op },
+        } => {
+            assert_eq!("tab", name.to_string());
+            assert_eq!("is_active", column_name.to_string());
+            let using_expr = Expr::Value(Value::SingleQuotedString("text".to_string()));
+            assert_eq!(
+                op,
+                AlterColumnOperation::SetDataType {
+                    data_type: DataType::Text,
+                    using: Some(using_expr),
+                }
+            );
+        }
+        _ => unreachable!(),
+    }
+}
+
 #[test]
 fn parse_create_table_if_not_exists() {
     let sql = "CREATE TABLE IF NOT EXISTS uk_cities ()";
@@ -749,6 +793,47 @@ fn test_transaction_statement() {
     );
 }
 
+#[test]
+fn parse_comments() {
+    match pg().verified_stmt("COMMENT ON COLUMN tab.name IS 'comment'") {
+        Statement::Comment {
+            object_type,
+            object_name,
+            comment: Some(comment),
+        } => {
+            assert_eq!("comment", comment);
+            assert_eq!("tab.name", object_name.to_string());
+            assert_eq!(CommentObject::Column, object_type);
+        }
+        _ => unreachable!(),
+    }
+
+    match pg().verified_stmt("COMMENT ON TABLE public.tab IS 'comment'") {
+        Statement::Comment {
+            object_type,
+            object_name,
+            comment: Some(comment),
+        } => {
+            assert_eq!("comment", comment);
+            assert_eq!("public.tab", object_name.to_string());
+            assert_eq!(CommentObject::Table, object_type);
+        }
+        _ => unreachable!(),
+    }
+
+    match pg().verified_stmt("COMMENT ON TABLE public.tab IS NULL") {
+        Statement::Comment {
+            object_type,
+            object_name,
+            comment: None,
+        } => {
+            assert_eq!("public.tab", object_name.to_string());
+            assert_eq!(CommentObject::Table, object_type);
+        }
+        _ => unreachable!(),
+    }
+}
+
 fn pg() -> TestedDialects {
     TestedDialects {
         dialects: vec![Box::new(PostgreSqlDialect {})],