diff --git a/src/ast/mod.rs b/src/ast/mod.rs
index eb5bc6cc75..cb74c04063 100644
--- a/src/ast/mod.rs
+++ b/src/ast/mod.rs
@@ -111,8 +111,8 @@ pub use self::query::{
     TableIndexHintType, TableIndexHints, TableIndexType, TableSample, TableSampleBucket,
     TableSampleKind, TableSampleMethod, TableSampleModifier, TableSampleQuantity, TableSampleSeed,
     TableSampleSeedModifier, TableSampleUnit, TableVersion, TableWithJoins, Top, TopQuantity,
-    UpdateTableFromKind, ValueTableMode, Values, WildcardAdditionalOptions, With, WithFill,
-    XmlNamespaceDefinition, XmlPassingArgument, XmlPassingClause, XmlTableColumn,
+    UpdateTableFromKind, ValueTableMode, Values, WildcardAdditionalOptions, With, WithExpression,
+    WithFill, XmlNamespaceDefinition, XmlPassingArgument, XmlPassingClause, XmlTableColumn,
     XmlTableColumnOption,
 };
 
diff --git a/src/ast/query.rs b/src/ast/query.rs
index 4aa82c7c3b..7d65d71174 100644
--- a/src/ast/query.rs
+++ b/src/ast/query.rs
@@ -753,8 +753,8 @@ pub struct With {
     pub with_token: AttachedToken,
     /// Whether the `WITH` is recursive (`WITH RECURSIVE`).
     pub recursive: bool,
-    /// The list of CTEs declared by this `WITH` clause.
-    pub cte_tables: Vec<Cte>,
+    /// The expressions declared by this `WITH` clause.
+    pub exprs: Vec<WithExpression>,
 }
 
 impl fmt::Display for With {
@@ -763,11 +763,40 @@ impl fmt::Display for With {
         if self.recursive {
             f.write_str("RECURSIVE ")?;
         }
-        display_comma_separated(&self.cte_tables).fmt(f)?;
+        display_comma_separated(&self.exprs).fmt(f)?;
         Ok(())
     }
 }
 
+/// A single expression in a `WITH` clause.
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum WithExpression {
+    /// A common table expression.
+    Cte(Cte),
+    /// A common scalar expression.
+    ///
+    /// [ClickHouse]: https://clickhouse.com/docs/sql-reference/statements/select/with#common-scalar-expressions
+    Cse(ExprWithAlias),
+    /// An XML namespace declaration list.
+    ///
+    /// [MSSQL]: https://learn.microsoft.com/en-us/sql/t-sql/xml/with-xmlnamespaces
+    XmlNamespaces(Vec<XmlNamespaceDefinition>),
+}
+
+impl fmt::Display for WithExpression {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            WithExpression::Cte(cte) => cte.fmt(f),
+            WithExpression::Cse(cse) => cse.fmt(f),
+            WithExpression::XmlNamespaces(namespaces) => {
+                write!(f, "XMLNAMESPACES ({})", display_comma_separated(namespaces))
+            }
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
diff --git a/src/ast/spans.rs b/src/ast/spans.rs
index 8267c71798..6c644f7cb5 100644
--- a/src/ast/spans.rs
+++ b/src/ast/spans.rs
@@ -47,7 +47,8 @@ use super::{
     ReplaceSelectItem, Select, SelectInto, SelectItem, SetExpr, Setting, SqlOption, Statement,
     Subscript, SymbolDefinition, TableAlias, TableAliasColumnDef, TableConstraint, TableFactor,
     TableObject, TableOptionsClustered, TableWithJoins, Update, UpdateTableFromKind, Use, Values,
-    ViewColumnDef, WhileStatement, WildcardAdditionalOptions, With, WithFill,
+    ViewColumnDef, WhileStatement, WildcardAdditionalOptions, With, WithExpression, WithFill,
+    XmlNamespaceDefinition,
 };
 
 /// Given an iterator of spans, return the [Span::union] of all spans.
@@ -185,12 +186,30 @@ impl Spanned for With {
         let With {
             with_token,
             recursive: _, // bool
-            cte_tables,
+            exprs,
         } = self;
 
-        union_spans(
-            core::iter::once(with_token.0.span).chain(cte_tables.iter().map(|item| item.span())),
-        )
+        union_spans(core::iter::once(with_token.0.span).chain(exprs.iter().map(|item| item.span())))
+    }
+}
+
+impl Spanned for WithExpression {
+    fn span(&self) -> Span {
+        match self {
+            WithExpression::Cte(cte) => cte.span(),
+            WithExpression::Cse(cse) => cse.span(),
+            WithExpression::XmlNamespaces(namespaces) => {
+                union_spans(namespaces.iter().map(|namespace| namespace.span()))
+            }
+        }
+    }
+}
+
+impl Spanned for XmlNamespaceDefinition {
+    fn span(&self) -> Span {
+        let XmlNamespaceDefinition { uri, name } = self;
+
+        union_spans(core::iter::once(uri.span()).chain(core::iter::once(name.span)))
     }
 }
 
@@ -2773,8 +2792,12 @@ pub mod tests {
         );
 
         let query = test.0.parse_query().unwrap();
-        let cte_span = query.clone().with.unwrap().cte_tables[0].span();
-        let cte_query_span = query.clone().with.unwrap().cte_tables[0].query.span();
+        let cte = match &query.with.as_ref().unwrap().exprs[0] {
+            WithExpression::Cte(cte) => cte,
+            _ => panic!("expected a CTE"),
+        };
+        let cte_span = cte.span();
+        let cte_query_span = cte.query.span();
         let body_span = query.body.span();
 
         // the WITH keyboard is part of the query
diff --git a/src/dialect/clickhouse.rs b/src/dialect/clickhouse.rs
index 41a0e8be42..11b4c28cd6 100644
--- a/src/dialect/clickhouse.rs
+++ b/src/dialect/clickhouse.rs
@@ -198,6 +198,11 @@ impl Dialect for ClickHouseDialect {
         true
     }
 
+    /// See <https://clickhouse.com/docs/sql-reference/statements/select/with#common-scalar-expressions>
+    fn supports_common_scalar_expressions(&self) -> bool {
+        true
+    }
+
     fn supports_comma_separated_trim(&self) -> bool {
         true
     }
diff --git a/src/dialect/mod.rs b/src/dialect/mod.rs
index a2920e61eb..6f1fcaa519 100644
--- a/src/dialect/mod.rs
+++ b/src/dialect/mod.rs
@@ -1985,6 +1985,18 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns true if the dialect supports Common Scalar Expressions in a `WITH` clause.
+    ///
+    /// For example:
+    /// ```sql
+    /// WITH 42 AS answer SELECT answer FROM t
+    /// ```
+    ///
+    /// [ClickHouse](https://clickhouse.com/docs/sql-reference/statements/select/with#common-scalar-expressions)
+    fn supports_common_scalar_expressions(&self) -> bool {
+        false
+    }
+
     /// Returns true if the dialect supports the two-argument comma-separated
     /// form of the `TRIM` function: `TRIM(expr, characters)`.
     fn supports_comma_separated_trim(&self) -> bool {
@@ -2029,11 +2041,24 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    // Returns true if the dialect supports a leading `WITH XMLNAMESPACES (...)`
+    /// clause in queries.
+    ///
+    /// Example:
+    /// ```sql
+    /// WITH XMLNAMESPACES ('urn:example' AS ns)
+    /// SELECT 1
+    /// ```
+    fn supports_with_xmlnamespaces_clause(&self) -> bool {
+        false
+    }
+    
     /// Returns true if the dialect supports aliased function arguments,
     /// e.g. `XMLFOREST(a AS x)` in PostgreSQL.
     fn supports_aliased_function_args(&self) -> bool {
         false
     }
+    
 
     /// Returns true if the dialect supports `USING <format>` in `CREATE TABLE`.
     ///
diff --git a/src/dialect/mssql.rs b/src/dialect/mssql.rs
index 06a07b61d8..b9734ae7a9 100644
--- a/src/dialect/mssql.rs
+++ b/src/dialect/mssql.rs
@@ -252,6 +252,11 @@ impl Dialect for MsSqlDialect {
             _ => None,
         }
     }
+
+    // see: https://learn.microsoft.com/en-us/sql/t-sql/xml/with-xmlnamespaces
+    fn supports_with_xmlnamespaces_clause(&self) -> bool {
+        true
+    }
 }
 
 impl MsSqlDialect {
diff --git a/src/parser/mod.rs b/src/parser/mod.rs
index 276b252ed2..2af0235c07 100644
--- a/src/parser/mod.rs
+++ b/src/parser/mod.rs
@@ -14878,11 +14878,11 @@ impl<'a> Parser<'a> {
     pub fn parse_query(&mut self) -> Result<Box<Query>, ParserError> {
         let _guard = self.recursion_counter.try_decrease()?;
         let with = if self.parse_keyword(Keyword::WITH) {
-            let with_token = self.get_current_token();
+            let with_token = self.get_current_token().clone();
             Some(With {
                 with_token: with_token.clone().into(),
                 recursive: self.parse_keyword(Keyword::RECURSIVE),
-                cte_tables: self.parse_comma_separated(Parser::parse_cte)?,
+                exprs: self.parse_comma_separated(Parser::parse_with_expression)?,
             })
         } else {
             None
@@ -15426,6 +15426,34 @@ impl<'a> Parser<'a> {
         Ok(cte)
     }
 
+    /// Parse a single expression in a `WITH` clause.
+    pub fn parse_with_expression(&mut self) -> Result<WithExpression, ParserError> {
+        if self.dialect.supports_with_xmlnamespaces_clause()
+            && self.parse_keyword(Keyword::XMLNAMESPACES)
+        {
+            self.expect_token(&Token::LParen)?;
+            let namespaces = self.parse_comma_separated(Parser::parse_xml_namespace_definition)?;
+            self.expect_token(&Token::RParen)?;
+            return Ok(WithExpression::XmlNamespaces(namespaces));
+        }
+
+        if !self.dialect.supports_common_scalar_expressions() {
+            return self.parse_cte().map(WithExpression::Cte);
+        }
+
+        if let Some(cte) = self.maybe_parse(|p| p.parse_cte())? {
+            return Ok(WithExpression::Cte(cte));
+        }
+
+        let expr = self.parse_expr()?;
+        self.expect_keyword(Keyword::AS)?;
+        let alias = self.parse_identifier()?;
+        Ok(WithExpression::Cse(ExprWithAlias {
+            expr,
+            alias: Some(alias),
+        }))
+    }
+
     /// Parse a "query body", which is an expression with roughly the
     /// following grammar:
     /// ```sql
diff --git a/tests/sqlparser_common.rs b/tests/sqlparser_common.rs
index 8f665b25c2..7f9532f07a 100644
--- a/tests/sqlparser_common.rs
+++ b/tests/sqlparser_common.rs
@@ -8149,18 +8149,21 @@ fn parse_ctes() {
 
     fn assert_ctes_in_select(expected: &[&str], sel: &Query) {
         for (i, exp) in expected.iter().enumerate() {
-            let Cte { alias, query, .. } = &sel.with.as_ref().unwrap().cte_tables[i];
-            assert_eq!(*exp, query.to_string());
-            assert_eq!(false, alias.explicit);
+            let cte = match &sel.with.as_ref().unwrap().exprs[i] {
+                WithExpression::Cte(cte) => cte,
+                other => panic!("expected a CTE, got {other:?}"),
+            };
+            assert_eq!(*exp, cte.query.to_string());
+            assert_eq!(false, cte.alias.explicit);
             assert_eq!(
                 if i == 0 {
                     Ident::new("a")
                 } else {
                     Ident::new("b")
                 },
-                alias.name
+                cte.alias.name
             );
-            assert!(alias.columns.is_empty());
+            assert!(cte.alias.columns.is_empty());
         }
     }
 
@@ -8193,26 +8196,29 @@ fn parse_ctes() {
     // CTE in a CTE...
     let sql = &format!("WITH outer_cte AS ({with}) SELECT * FROM outer_cte");
     let select = verified_query(sql);
-    assert_ctes_in_select(&cte_sqls, &only(&select.with.unwrap().cte_tables).query);
+    let with = select.with.as_ref().unwrap();
+    let outer_cte = match only(&with.exprs) {
+        WithExpression::Cte(cte) => cte,
+        other => panic!("expected a CTE, got {other:?}"),
+    };
+    assert_ctes_in_select(&cte_sqls, &outer_cte.query);
 }
 
 #[test]
 fn parse_cte_renamed_columns() {
     let sql = "WITH cte (col1, col2) AS (SELECT foo, bar FROM baz) SELECT * FROM cte";
     let query = all_dialects().verified_query(sql);
+    let with = query.with.unwrap();
+    let cte = match with.exprs.first().unwrap() {
+        WithExpression::Cte(cte) => cte,
+        other => panic!("expected a CTE, got {other:?}"),
+    };
     assert_eq!(
         vec![
             TableAliasColumnDef::from_name("col1"),
             TableAliasColumnDef::from_name("col2")
         ],
-        query
-            .with
-            .unwrap()
-            .cte_tables
-            .first()
-            .unwrap()
-            .alias
-            .columns
+        cte.alias.columns
     );
 }
 
@@ -8226,8 +8232,8 @@ fn parse_recursive_cte() {
 
     let with = query.with.as_ref().unwrap();
     assert!(with.recursive);
-    assert_eq!(with.cte_tables.len(), 1);
-    let expected = Cte {
+    assert_eq!(with.exprs.len(), 1);
+    let expected = WithExpression::Cte(Cte {
         alias: TableAlias {
             explicit: false,
             name: Ident {
@@ -8242,8 +8248,8 @@ fn parse_recursive_cte() {
         from: None,
         materialized: None,
         closing_paren_token: AttachedToken::empty(),
-    };
-    assert_eq!(with.cte_tables.first().unwrap(), &expected);
+    });
+    assert_eq!(with.exprs.first().unwrap(), &expected);
 }
 
 #[test]
@@ -20865,11 +20871,16 @@ fn parse_cte_materialization() {
         let sql = format!("WITH c AS {directive}(SELECT 1) SELECT * FROM c");
         TestedDialects::new(vec![Box::new(DuckDbDialect {})]).verified_query(&sql);
         let query = all_dialects_where(|d| d.supports_cte_materialization()).verified_query(&sql);
-        assert_eq!(query.with.unwrap().cte_tables[0].materialized, expected);
+        let with = query.with.unwrap();
+        let cte = match &with.exprs[0] {
+            WithExpression::Cte(cte) => cte,
+            other => panic!("expected a CTE, got {other:?}"),
+        };
+        assert_eq!(cte.materialized, expected);
         if expected.is_some() {
-            all_dialects_where(|d| !d.supports_cte_materialization())
-                .parse_sql_statements(&sql)
-                .unwrap_err();
+            for dialect in all_dialects_where(|d| !d.supports_cte_materialization()).dialects {
+                Parser::parse_sql(dialect.as_ref(), &sql).unwrap_err();
+            }
         }
     }
 }
diff --git a/tests/sqlparser_mssql.rs b/tests/sqlparser_mssql.rs
index 9bf015fc00..56561154c9 100644
--- a/tests/sqlparser_mssql.rs
+++ b/tests/sqlparser_mssql.rs
@@ -31,7 +31,7 @@ use sqlparser::ast::DataType::{Int, Text, Varbinary};
 use sqlparser::ast::DeclareAssignment::MsSqlAssignment;
 use sqlparser::ast::Value::SingleQuotedString;
 use sqlparser::ast::*;
-use sqlparser::dialect::{GenericDialect, MsSqlDialect};
+use sqlparser::dialect::{Dialect, GenericDialect, MsSqlDialect};
 use sqlparser::parser::{Parser, ParserError, ParserOptions};
 
 #[test]
@@ -2969,6 +2969,39 @@ fn parse_mssql_money_constants() {
     );
 }
 
+#[test]
+fn parse_xmlnamespaces() {
+    let sql =
+        "WITH XMLNAMESPACES ('urn:test' AS ns) SELECT 1 AS [ns:Value] FOR XML PATH('ns:Root')";
+    let query = ms().verified_query(sql);
+    let with = query.with.as_ref().unwrap();
+    assert_eq!(with.exprs.len(), 1);
+    assert_eq!(with.to_string(), "WITH XMLNAMESPACES ('urn:test' AS ns)");
+    assert_eq!(
+        with.exprs[0].to_string(),
+        "XMLNAMESPACES ('urn:test' AS ns)"
+    );
+    assert_eq!(query.to_string(), sql);
+    assert_eq!(with.span(), Span::empty());
+    match &with.exprs[0] {
+        WithExpression::XmlNamespaces(namespaces) => {
+            assert_eq!(namespaces.len(), 1);
+            assert_eq!(namespaces[0].to_string(), "'urn:test' AS ns");
+            assert_eq!(namespaces[0].span(), Span::empty());
+        }
+        other => panic!("expected XMLNAMESPACES, got {other:?}"),
+    }
+
+    let query = ms().verified_query(
+        "WITH XMLNAMESPACES ('urn:example' AS ns), t AS (SELECT 1 AS id) SELECT id FROM t",
+    );
+    let with = query.with.as_ref().unwrap();
+    assert_eq!(with.exprs.len(), 2);
+    assert!(matches!(with.exprs[0], WithExpression::XmlNamespaces(_)));
+    assert!(matches!(with.exprs[1], WithExpression::Cte(_)));
+    assert!(!GenericDialect {}.supports_with_xmlnamespaces_clause());
+}
+
 #[test]
 fn parse_bracket_quoted_function_argument_name() {
     let Statement::DropFunction(drop) = ms().verified_stmt("DROP FUNCTION f([Role] INT)") else {