diff --git a/sql-to-dbsp-compiler/SQL-compiler/src/main/java/org/dbsp/sqlCompiler/compiler/frontend/AggregateCompiler.java b/sql-to-dbsp-compiler/SQL-compiler/src/main/java/org/dbsp/sqlCompiler/compiler/frontend/AggregateCompiler.java
index 0fdf600969b..d55c93c9f27 100644
--- a/sql-to-dbsp-compiler/SQL-compiler/src/main/java/org/dbsp/sqlCompiler/compiler/frontend/AggregateCompiler.java
+++ b/sql-to-dbsp-compiler/SQL-compiler/src/main/java/org/dbsp/sqlCompiler/compiler/frontend/AggregateCompiler.java
@@ -405,8 +405,8 @@ void processSingle(SqlSingleValueAggFunction function) {
         DBSPExpression increment = aggregatedValue;
         if (!increment.getType().mayBeNull)
             increment = increment.some();
-        DBSPType semigroup = new DBSPTypeUser(CalciteObject.EMPTY, SEMIGROUP, "DefaultOptSemigroup",
-                false, accumulator.getType().setMayBeNull(false));
+        DBSPType semigroup = new DBSPTypeUser(CalciteObject.EMPTY, SEMIGROUP, "UnimplementedSemigroup",
+                false, accumulator.getType());
         this.setFoldingFunction(new DBSPAggregate.Implementation(
                 node, zero, this.makeRowClosure(increment, accumulator), zero, semigroup, null));
     }
diff --git a/sql-to-dbsp-compiler/SQL-compiler/src/test/java/org/dbsp/sqlCompiler/compiler/sql/simple/TimeTests.java b/sql-to-dbsp-compiler/SQL-compiler/src/test/java/org/dbsp/sqlCompiler/compiler/sql/simple/TimeTests.java
index 82fbe4d569f..b3bd703beb1 100644
--- a/sql-to-dbsp-compiler/SQL-compiler/src/test/java/org/dbsp/sqlCompiler/compiler/sql/simple/TimeTests.java
+++ b/sql-to-dbsp-compiler/SQL-compiler/src/test/java/org/dbsp/sqlCompiler/compiler/sql/simple/TimeTests.java
@@ -64,6 +64,31 @@ public Change createInput() {
         return new Change(new DBSPZSetLiteral(new DBSPTupleExpression(new DBSPTimestampLiteral(100))));
     }
 
+    @Test
+    public void issue1843() {
+        String sql = """
+                create table credit_card_transactions(transaction_time timestamp);
+                
+                create table my_timer(t timestamp);\s
+                
+                create view recent_transactions as
+                SELECT * FROM credit_card_transactions
+                WHERE transaction_time >= (SELECT t FROM my_timer) - INTERVAL 1 DAY;""";
+        this.compileRustTestCase(sql);
+    }
+
+    @Test
+    public void issue1844() {
+        String sql = """
+                create table credit_card_transactions(transaction_time timestamp);
+                create table my_timer(id int primary key, t timestamp);\s
+                
+                create view recent_transactions as
+                SELECT * FROM credit_card_transactions
+                WHERE transaction_time >= (SELECT DATE_SUB(t, INTERVAL 1 DAY) FROM my_timer);""";
+        this.compileRustTestCase(sql);
+    }
+
     @Test
     public void testInterval() {
         this.testQuery("SELECT INTERVAL '20' YEAR",
diff --git a/sql-to-dbsp-compiler/lib/sqllib/src/timestamp.rs b/sql-to-dbsp-compiler/lib/sqllib/src/timestamp.rs
index 8c4084a4237..7bb5f37bbfe 100644
--- a/sql-to-dbsp-compiler/lib/sqllib/src/timestamp.rs
+++ b/sql-to-dbsp-compiler/lib/sqllib/src/timestamp.rs
@@ -275,6 +275,14 @@ polymorphic_return_function2!(
     Timestamp
 );
 
+pub fn minus_Date_ShortInterval_Date(left: Date, right: ShortInterval) -> Date {
+    let days = (right.milliseconds() / (86400 * 1000)) as i32;
+    let diff = left.days() - days;
+    Date::new(diff)
+}
+
+polymorphic_return_function2!(minus, Date, Date, ShortInterval, ShortInterval, Date, Date);
+
 pub fn minus_Timestamp_Timestamp_LongInterval(left: Timestamp, right: Timestamp) -> LongInterval {
     let ldate = left.to_dateTime();
     let rdate = right.to_dateTime();