From 10c69b910ec3fbb74036b282b7b16bd3b68bc1b3 Mon Sep 17 00:00:00 2001
From: PThorpe92 <preston@turso.tech>
Date: Thu, 16 Oct 2025 16:39:10 -0400
Subject: [PATCH 1/3] Prevent ambiguous self-join table reference

---
 core/translate/select.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/core/translate/select.rs b/core/translate/select.rs
index 59b6ff6cb..376745f77 100644
--- a/core/translate/select.rs
+++ b/core/translate/select.rs
@@ -225,6 +225,16 @@ fn prepare_one_select_plan(
                 &mut table_references,
                 connection,
             )?;
+            // Validate that all table references have unique identifiers
+            let mut seen_identifiers = std::collections::HashSet::new();
+            for table in table_references.joined_tables().iter() {
+                if !seen_identifiers.insert(&table.identifier) {
+                    crate::bail_parse_error!(
+                "table name {} specified more than once - use aliases to distinguish multiple references",
+                table.identifier
+            );
+                }
+            }
 
             // Preallocate space for the result columns
             let result_columns = Vec::with_capacity(

From 79c5234122ccb4c22e49930c28d1a8ca7bbc74fa Mon Sep 17 00:00:00 2001
From: PThorpe92 <preston@turso.tech>
Date: Thu, 16 Oct 2025 16:43:08 -0400
Subject: [PATCH 2/3] Add TCL test for self ambiguous join

---
 testing/select.test | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/testing/select.test b/testing/select.test
index 72688913c..c42e38e42 100755
--- a/testing/select.test
+++ b/testing/select.test
@@ -1074,3 +1074,23 @@ do_execsql_test_on_specific_db {:memory:} rowid-select-from-clause-subquery-expl
 	SELECT rowid,a FROM (SELECT rowid,a FROM t);
 } {1|abc}
 
+# https://github.com/tursodatabase/turso/issues/3505 regression test
+do_execsql_test_in_memory_any_error ambiguous-self-join {
+    CREATE TABLE T(a);
+	INSERT INTO t VALUES (1), (2), (3); 
+	SELECT * fROM t JOIN t;
+}
+
+do_execsql_test_on_specific_db {:memory:} unambiguous-self-join {
+    CREATE TABLE T(a);
+	INSERT INTO t VALUES (1), (2), (3); 
+	SELECT * fROM t as ta JOIN t order by ta.a;
+} {1|1
+1|2
+1|3
+2|1
+2|2
+2|3
+3|1
+3|2
+3|3}

From ddd674c34012e1a587a4c44006c4fd97e254775e Mon Sep 17 00:00:00 2001
From: PThorpe92 <preston@turso.tech>
Date: Thu, 16 Oct 2025 18:32:48 -0400
Subject: [PATCH 3/3] Move duplicate table identifier checking to parse_join to
 allow for natural joins

---
 core/translate/planner.rs | 22 +++++++++++++++++++++-
 core/translate/select.rs  | 10 ----------
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/core/translate/planner.rs b/core/translate/planner.rs
index 08936abf3..f7d930bd6 100644
--- a/core/translate/planner.rs
+++ b/core/translate/planner.rs
@@ -986,9 +986,29 @@ fn parse_join(
         crate::bail_parse_error!("NATURAL JOIN cannot be combined with ON or USING clause");
     }
 
+    // this is called once for each join, so we only need to check the rightmost table
+    // against all previous tables for duplicates
+    let rightmost_table = table_references.joined_tables().last().unwrap();
+    let has_duplicate = table_references
+        .joined_tables()
+        .iter()
+        .take(table_references.joined_tables().len() - 1)
+        .any(|t| t.identifier == rightmost_table.identifier);
+
+    if has_duplicate
+        && !natural
+        && constraint
+            .as_ref()
+            .is_none_or(|c| !matches!(c, ast::JoinConstraint::Using(_)))
+    {
+        // Duplicate table names are only allowed for NATURAL or USING joins
+        crate::bail_parse_error!(
+            "table name {} specified more than once - use an alias to disambiguate",
+            rightmost_table.identifier
+        );
+    }
     let constraint = if natural {
         assert!(table_references.joined_tables().len() >= 2);
-        let rightmost_table = table_references.joined_tables().last().unwrap();
         // NATURAL JOIN is first transformed into a USING join with the common columns
         let mut distinct_names: Vec<ast::Name> = vec![];
         // TODO: O(n^2) maybe not great for large tables or big multiway joins
diff --git a/core/translate/select.rs b/core/translate/select.rs
index 376745f77..59b6ff6cb 100644
--- a/core/translate/select.rs
+++ b/core/translate/select.rs
@@ -225,16 +225,6 @@ fn prepare_one_select_plan(
                 &mut table_references,
                 connection,
             )?;
-            // Validate that all table references have unique identifiers
-            let mut seen_identifiers = std::collections::HashSet::new();
-            for table in table_references.joined_tables().iter() {
-                if !seen_identifiers.insert(&table.identifier) {
-                    crate::bail_parse_error!(
-                "table name {} specified more than once - use aliases to distinguish multiple references",
-                table.identifier
-            );
-                }
-            }
 
             // Preallocate space for the result columns
             let result_columns = Vec::with_capacity(