don't allow duplicate col names in create table

core/translate/schema.rs

@@ -40,6 +40,19 @@ pub fn translate_create_table(
         bail_parse_error!("TEMPORARY table not supported yet");
     }
 
+    // maybe we can do better than this.
+    if let ast::CreateTableBody::ColumnsAndConstraints { columns, .. } = &body {
+        for i in 0..columns.len() {
+            let name1 = normalize_ident(columns[i].col_name.as_str());
+            for j in (i + 1)..columns.len() {
+                let name2 = normalize_ident(columns[j].col_name.as_str());
+                if name1 == name2 {
+                    bail_parse_error!("duplicate column name: {}", columns[i].col_name.as_str());
+                }
+            }
+        }
+    }
+
     // Check for STRICT mode without experimental flag
     if let ast::CreateTableBody::ColumnsAndConstraints { options, .. } = &body {
         if options.contains(ast::TableOptions::STRICT) && !connection.experimental_strict_enabled()

testing/create_table.test

@@ -53,3 +53,8 @@ do_execsql_test_on_specific_db {:memory:} col-named-rowid {
   update t set rowid = 1; -- should allow regular update and not throw unique constraint
   select count(*) from t where rowid = 1;
 } {3}
+
+# https://github.com/tursodatabase/turso/issues/3637
+do_execsql_test_in_memory_any_error create_table_duplicate_column_names {
+    CREATE TABLE t(a, a);
+}