diff --git a/core/translate/optimizer/constraints.rs b/core/translate/optimizer/constraints.rs
index 486c36687..a1740f2f9 100644
--- a/core/translate/optimizer/constraints.rs
+++ b/core/translate/optimizer/constraints.rs
@@ -9,7 +9,7 @@ use crate::{
     translate::{
         collate::get_collseq_from_expr,
         expr::as_binary_components,
-        plan::{JoinOrderMember, TableReferences, WhereTerm},
+        plan::{JoinOrderMember, NonFromClauseSubquery, TableReferences, WhereTerm},
         planner::{table_mask_from_expr, TableMask},
     },
     util::exprs_are_equivalent,
@@ -188,6 +188,7 @@ pub fn constraints_from_where_clause(
     where_clause: &[WhereTerm],
     table_references: &TableReferences,
     available_indexes: &HashMap<String, VecDeque<Arc<Index>>>,
+    subqueries: &[NonFromClauseSubquery],
 ) -> Result<Vec<TableConstraints>> {
     let mut constraints = Vec::new();
 
@@ -241,7 +242,7 @@ pub fn constraints_from_where_clause(
                             where_clause_pos: (i, BinaryExprSide::Rhs),
                             operator,
                             table_col_pos: *column,
-                            lhs_mask: table_mask_from_expr(rhs, table_references)?,
+                            lhs_mask: table_mask_from_expr(rhs, table_references, subqueries)?,
                             selectivity: estimate_selectivity(table_column, operator),
                             usable: true,
                         });
@@ -258,7 +259,7 @@ pub fn constraints_from_where_clause(
                             where_clause_pos: (i, BinaryExprSide::Rhs),
                             operator,
                             table_col_pos: rowid_alias_column.unwrap(),
-                            lhs_mask: table_mask_from_expr(rhs, table_references)?,
+                            lhs_mask: table_mask_from_expr(rhs, table_references, subqueries)?,
                             selectivity: estimate_selectivity(table_column, operator),
                             usable: true,
                         });
@@ -274,7 +275,7 @@ pub fn constraints_from_where_clause(
                             where_clause_pos: (i, BinaryExprSide::Lhs),
                             operator: opposite_cmp_op(operator),
                             table_col_pos: *column,
-                            lhs_mask: table_mask_from_expr(lhs, table_references)?,
+                            lhs_mask: table_mask_from_expr(lhs, table_references, subqueries)?,
                             selectivity: estimate_selectivity(table_column, operator),
                             usable: true,
                         });
@@ -288,7 +289,7 @@ pub fn constraints_from_where_clause(
                             where_clause_pos: (i, BinaryExprSide::Lhs),
                             operator: opposite_cmp_op(operator),
                             table_col_pos: rowid_alias_column.unwrap(),
-                            lhs_mask: table_mask_from_expr(lhs, table_references)?,
+                            lhs_mask: table_mask_from_expr(lhs, table_references, subqueries)?,
                             selectivity: estimate_selectivity(table_column, operator),
                             usable: true,
                         });
diff --git a/core/translate/optimizer/join.rs b/core/translate/optimizer/join.rs
index 79b80174a..89e5d7d3f 100644
--- a/core/translate/optimizer/join.rs
+++ b/core/translate/optimizer/join.rs
@@ -540,9 +540,13 @@ mod tests {
         let where_clause = vec![];
 
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let result = compute_best_join_order(
             table_references.joined_tables(),
@@ -569,9 +573,13 @@ mod tests {
         let where_clause = vec![];
 
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         // SELECT * from test_table
         // expecting best_best_plan() not to do any work due to empty where clause.
@@ -610,9 +618,13 @@ mod tests {
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
         let available_indexes = HashMap::new();
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         // SELECT * FROM test_table WHERE id = 42
         // expecting a RowidEq access method because id is a rowid alias.
@@ -678,9 +690,13 @@ mod tests {
         });
         available_indexes.insert("test_table".to_string(), VecDeque::from([index]));
 
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
         // SELECT * FROM test_table WHERE id = 42
         // expecting an IndexScan access method because id is a primary key with an index
         let result = compute_best_join_order(
@@ -757,9 +773,13 @@ mod tests {
 
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let result = compute_best_join_order(
             table_references.joined_tables(),
@@ -932,9 +952,13 @@ mod tests {
 
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let result = compute_best_join_order(
             table_references.joined_tables(),
@@ -1041,9 +1065,13 @@ mod tests {
         let table_references = TableReferences::new(joined_tables, vec![]);
         let available_indexes = HashMap::new();
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let BestJoinOrderResult { best_plan, .. } = compute_best_join_order(
             table_references.joined_tables(),
@@ -1147,9 +1175,13 @@ mod tests {
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
         let available_indexes = HashMap::new();
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let result = compute_best_join_order(
             table_references.joined_tables(),
@@ -1231,9 +1263,13 @@ mod tests {
 
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         // Run the optimizer
         let BestJoinOrderResult { best_plan, .. } = compute_best_join_order(
@@ -1352,9 +1388,13 @@ mod tests {
 
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let BestJoinOrderResult { best_plan, .. } = compute_best_join_order(
             table_references.joined_tables(),
@@ -1460,9 +1500,13 @@ mod tests {
 
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let BestJoinOrderResult { best_plan, .. } = compute_best_join_order(
             table_references.joined_tables(),
@@ -1586,9 +1630,13 @@ mod tests {
 
         let table_references = TableReferences::new(joined_tables, vec![]);
         let access_methods_arena = RefCell::new(Vec::new());
-        let table_constraints =
-            constraints_from_where_clause(&where_clause, &table_references, &available_indexes)
-                .unwrap();
+        let table_constraints = constraints_from_where_clause(
+            &where_clause,
+            &table_references,
+            &available_indexes,
+            &[],
+        )
+        .unwrap();
 
         let BestJoinOrderResult { best_plan, .. } = compute_best_join_order(
             table_references.joined_tables(),
diff --git a/core/translate/optimizer/mod.rs b/core/translate/optimizer/mod.rs
index 0b6042687..32e7868f5 100644
--- a/core/translate/optimizer/mod.rs
+++ b/core/translate/optimizer/mod.rs
@@ -23,8 +23,8 @@ use crate::{
             constraints::{RangeConstraintRef, SeekRangeConstraint, TableConstraints},
         },
         plan::{
-            ColumnUsedMask, OuterQueryReference, QueryDestination, ResultSetColumn, Scan,
-            SeekKeyComponent,
+            ColumnUsedMask, NonFromClauseSubquery, OuterQueryReference, QueryDestination,
+            ResultSetColumn, Scan, SeekKeyComponent,
         },
     },
     types::SeekOp,
@@ -89,6 +89,7 @@ pub fn optimize_select_plan(plan: &mut SelectPlan, schema: &Schema) -> Result<()
         &mut plan.where_clause,
         &mut plan.order_by,
         &mut plan.group_by,
+        &plan.non_from_clause_subqueries,
     )?;
 
     if let Some(best_join_order) = best_join_order {
@@ -114,6 +115,7 @@ fn optimize_delete_plan(plan: &mut DeletePlan, schema: &Schema) -> Result<()> {
         &mut plan.where_clause,
         &mut plan.order_by,
         &mut None,
+        &[],
     )?;
 
     Ok(())
@@ -138,6 +140,7 @@ fn optimize_update_plan(
         &mut plan.where_clause,
         &mut plan.order_by,
         &mut None,
+        &[],
     )?;
 
     let table_ref = &mut plan.table_references.joined_tables_mut()[0];
@@ -337,6 +340,7 @@ fn optimize_table_access(
     where_clause: &mut [WhereTerm],
     order_by: &mut Vec<(Box<ast::Expr>, SortOrder)>,
     group_by: &mut Option<GroupBy>,
+    subqueries: &[NonFromClauseSubquery],
 ) -> Result<Option<Vec<JoinOrderMember>>> {
     if table_references.joined_tables().len() > TableReferences::MAX_JOINED_TABLES {
         crate::bail_parse_error!(
@@ -346,8 +350,12 @@ fn optimize_table_access(
     }
     let access_methods_arena = RefCell::new(Vec::new());
     let maybe_order_target = compute_order_target(order_by, group_by.as_mut());
-    let constraints_per_table =
-        constraints_from_where_clause(where_clause, table_references, available_indexes)?;
+    let constraints_per_table = constraints_from_where_clause(
+        where_clause,
+        table_references,
+        available_indexes,
+        subqueries,
+    )?;
 
     // Currently the expressions we evaluate as constraints are binary expressions that will never be true for a NULL operand.
     // If there are any constraints on the right hand side table of an outer join that are not part of the outer join condition,
@@ -806,7 +814,9 @@ impl Optimizable for ast::Expr {
                     return true;
                 }
 
-                let table_ref = tables.find_joined_table_by_internal_id(*table).unwrap();
+                let (_, table_ref) = tables
+                    .find_table_by_internal_id(*table)
+                    .expect("table not found");
                 let columns = table_ref.columns();
                 let column = &columns[*column];
                 column.primary_key || column.notnull
diff --git a/core/translate/planner.rs b/core/translate/planner.rs
index f47d4afdb..0409ae786 100644
--- a/core/translate/planner.rs
+++ b/core/translate/planner.rs
@@ -891,6 +891,7 @@ impl TableMask {
 pub fn table_mask_from_expr(
     top_level_expr: &Expr,
     table_references: &TableReferences,
+    subqueries: &[NonFromClauseSubquery],
 ) -> Result<TableMask> {
     let mut mask = TableMask::new();
     walk_expr(top_level_expr, &mut |expr: &Expr| -> Result<WalkControl> {
@@ -912,6 +913,34 @@ pub fn table_mask_from_expr(
                     crate::bail_parse_error!("table not found in joined_tables");
                 }
             }
+            // Given something like WHERE t.a = (SELECT ...), we can only evaluate that expression
+            // when all both table 't' and all outer scope tables referenced by the subquery OR its nested subqueries are in scope.
+            // Hence, the tables referenced in subqueries must be added to the table mask.
+            Expr::SubqueryResult { subquery_id, .. } => {
+                let Some(subquery) = subqueries.iter().find(|s| s.internal_id == *subquery_id)
+                else {
+                    crate::bail_parse_error!("subquery not found");
+                };
+                let SubqueryState::Unevaluated { plan } = &subquery.state else {
+                    crate::bail_parse_error!("subquery has already been evaluated");
+                };
+                let used_outer_query_refs = plan
+                    .as_ref()
+                    .unwrap()
+                    .table_references
+                    .outer_query_refs()
+                    .iter()
+                    .filter(|t| t.is_used());
+                for outer_query_ref in used_outer_query_refs {
+                    if let Some(table_idx) = table_references
+                        .joined_tables()
+                        .iter()
+                        .position(|t| t.internal_id == outer_query_ref.internal_id)
+                    {
+                        mask.add_table(table_idx);
+                    }
+                }
+            }
             _ => {}
         }
         Ok(WalkControl::Continue)
diff --git a/core/translate/select.rs b/core/translate/select.rs
index 60583a52c..0c9ebf2de 100644
--- a/core/translate/select.rs
+++ b/core/translate/select.rs
@@ -503,7 +503,6 @@ fn prepare_one_select_plan(
                     &mut windows,
                 )?;
             }
-        
 
             // TODO: support subqueries in the following positions:
             // - result column of a select, e.g.: SELECT x = (SELECT ...) FROM t