diff --git a/storm-core/src/main/java/st/orm/core/template/Query.java b/storm-core/src/main/java/st/orm/core/template/Query.java
index 4dcdd940..8161538f 100644
--- a/storm-core/src/main/java/st/orm/core/template/Query.java
+++ b/storm-core/src/main/java/st/orm/core/template/Query.java
@@ -278,10 +278,18 @@ default <T extends Data> List<Ref<T>> getRefList(@Nonnull Class<T> type, @Nonnul
      */
     private <T> T singleResult(@Nonnull Stream<T> stream) {
         try (stream) {
-            return stream
-                    .reduce((a, b) -> {
-                        throw new NonUniqueResultException("Expected single result, but found more than one.");
-                    }).orElseThrow(() -> new NoResultException("Expected single result, but found none."));
+            var iterator = stream.iterator();
+            if (!iterator.hasNext()) {
+                throw new NoResultException("Expected single result, but found none.");
+            }
+            T result = iterator.next();
+            if (iterator.hasNext()) {
+                throw new NonUniqueResultException("Expected single result, but found more than one.");
+            }
+            if (result == null) {
+                throw new PersistenceException("Expected single result, but found null. Wrap the field in COALESCE() to provide a non-null default.");
+            }
+            return result;
         }
     }
 
@@ -289,16 +297,25 @@ private <T> T singleResult(@Nonnull Stream<T> stream) {
      * Returns the single result of the stream, or an empty optional if there is no result.
      *
      * @param stream the stream to get the single result from.
-     * @return the single result of the stream.
      * @param <T> the type of the result.
+     * @return the single result of the stream.
      * @throws NonUniqueResultException if more than one result.
+     * @throws PersistenceException if the single row's value is null.
      */
     private <T> Optional<T> optionalResult(@Nonnull Stream<T> stream) {
         try (stream) {
-            return stream
-                    .reduce((a, b) -> {
-                        throw new NonUniqueResultException("Expected single result, but found more than one.");
-                    });
+            var iterator = stream.iterator();
+            if (!iterator.hasNext()) {
+                return Optional.empty();
+            }
+            T result = iterator.next();
+            if (iterator.hasNext()) {
+                throw new NonUniqueResultException("Expected single result, but found more than one.");
+            }
+            if (result == null) {
+                throw new PersistenceException("Result is null. Wrap the field in COALESCE() to provide a non-null default.");
+            }
+            return Optional.of(result);
         }
     }
 }
diff --git a/storm-core/src/main/java/st/orm/core/template/QueryBuilder.java b/storm-core/src/main/java/st/orm/core/template/QueryBuilder.java
index cdbb970f..1bc1cd73 100644
--- a/storm-core/src/main/java/st/orm/core/template/QueryBuilder.java
+++ b/storm-core/src/main/java/st/orm/core/template/QueryBuilder.java
@@ -946,29 +946,46 @@ public final List<R> getResultList() {
      * @return the single result.
      * @throws NoResultException if there is no result.
      * @throws NonUniqueResultException if more than one result.
-     * @throws PersistenceException if the query fails.
+     * @throws PersistenceException if the single row's value is null, or the query fails.
      */
     public final R getSingleResult() {
         try (var stream = getResultStream()) {
-            return stream
-                    .reduce((a, b) -> {
-                        throw new NonUniqueResultException("Expected single result, but found more than one.");
-                    }).orElseThrow(() -> new NoResultException("Expected single result, but found none."));
+            var iterator = stream.iterator();
+            if (!iterator.hasNext()) {
+                throw new NoResultException("Expected single result, but found none.");
+            }
+            R result = iterator.next();
+            if (iterator.hasNext()) {
+                throw new NonUniqueResultException("Expected single result, but found more than one.");
+            }
+            if (result == null) {
+                throw new PersistenceException("Expected single result, but found null. Wrap the field in COALESCE() to provide a non-null default.");
+            }
+            return result;
         }
     }
 
     /**
      * Executes the query and returns an optional result.
      *
-     * @return the optional result.
+     * @return the optional result; {@link Optional#empty()} when no row matched.
      * @throws NonUniqueResultException if more than one result.
-     * @throws PersistenceException if the query fails.
+     * @throws PersistenceException if the single row's value is null, or the query fails.
      */
     public final Optional<R> getOptionalResult() {
         try (var stream = getResultStream()) {
-            return stream.reduce((a, b) -> {
+            var iterator = stream.iterator();
+            if (!iterator.hasNext()) {
+                return Optional.empty();
+            }
+            R result = iterator.next();
+            if (iterator.hasNext()) {
                 throw new NonUniqueResultException("Expected single result, but found more than one.");
-            });
+            }
+            if (result == null) {
+                throw new PersistenceException("Result is null. Wrap the field in COALESCE() to provide a non-null default.");
+            }
+            return Optional.of(result);
         }
     }
 
diff --git a/storm-kotlin/src/main/kotlin/st/orm/template/Query.kt b/storm-kotlin/src/main/kotlin/st/orm/template/Query.kt
index 749b26ae..8499f888 100644
--- a/storm-kotlin/src/main/kotlin/st/orm/template/Query.kt
+++ b/storm-kotlin/src/main/kotlin/st/orm/template/Query.kt
@@ -20,8 +20,8 @@ import kotlinx.coroutines.stream.consumeAsFlow
 import st.orm.Data
 import st.orm.NoResultException
 import st.orm.NonUniqueResultException
+import st.orm.PersistenceException
 import st.orm.Ref
-import java.util.function.Supplier
 import java.util.stream.Stream
 import kotlin.reflect.KClass
 
@@ -318,29 +318,49 @@ interface Query {
      */
     private fun <T> singleResult(stream: Stream<T>): T {
         stream.use {
-            return stream
-                .reduce { _, _ ->
-                    throw NonUniqueResultException("Expected single result, but found more than one.")
-                }
-                .orElseThrow(Supplier { NoResultException("Expected single result, but found none.") })
+            val iterator = stream.iterator()
+            if (!iterator.hasNext()) {
+                throw NoResultException("Expected single result, but found none.")
+            }
+            val result = iterator.next()
+            if (iterator.hasNext()) {
+                throw NonUniqueResultException("Expected single result, but found more than one.")
+            }
+            if (result == null) {
+                throw PersistenceException("Expected single result, but found null. Wrap the field in COALESCE() to provide a non-null default.")
+            }
+            return result
         }
     }
 
     /**
-     * Returns the single result of the stream, or an empty optional if there is no result.
+     * Returns the single result of the stream, or `null` if there is no result.
+     *
+     * Iterates the stream explicitly rather than using [Stream.reduce] — the standard reduce internally
+     * calls `Optional.of(element)`, which throws a message-less [NullPointerException] when the only
+     * element is `null`. The iterator form lets the method detect that case and report it via a typed
+     * [PersistenceException] with a clear message.
      *
      * @param stream the stream to get the single result from.
-     * @return the single result of the stream.
      * @param <T> the type of the result.
+     * @return the single result of the stream, or `null` when no row matched.
      * @throws NonUniqueResultException if more than one result.
+     * @throws PersistenceException if the single row's value is SQL NULL.
      */
     private fun <T> optionalResult(stream: Stream<T>): T? {
         stream.use {
-            return stream
-                .reduce { _, _ ->
-                    throw NonUniqueResultException("Expected single result, but found more than one.")
-                }
-                .orElse(null)
+            val iterator = stream.iterator()
+            if (!iterator.hasNext()) {
+                return null
+            }
+            val result = iterator.next()
+            if (iterator.hasNext()) {
+                throw NonUniqueResultException("Expected single result, but found more than one.")
+            }
+            if (result == null) {
+                throw PersistenceException("Result is null. Wrap the field in COALESCE() to provide a non-null default.")
+            }
+            return result
         }
     }
 }
diff --git a/storm-kotlin/src/main/kotlin/st/orm/template/QueryBuilder.kt b/storm-kotlin/src/main/kotlin/st/orm/template/QueryBuilder.kt
index 35a02afd..8aae989e 100644
--- a/storm-kotlin/src/main/kotlin/st/orm/template/QueryBuilder.kt
+++ b/storm-kotlin/src/main/kotlin/st/orm/template/QueryBuilder.kt
@@ -25,7 +25,6 @@ import st.orm.template.TemplateString.Companion.raw
 import st.orm.template.TemplateString.Companion.wrap
 import st.orm.template.impl.create
 import st.orm.template.impl.createRef
-import java.util.function.Supplier
 import java.util.stream.Stream
 import kotlin.reflect.KClass
 
@@ -1015,15 +1014,22 @@ interface QueryBuilder<T : Data, R, ID> {
          * @return the single result.
          * @throws NoResultException if there is no result.
          * @throws NonUniqueResultException if more than one result.
-         * @throws PersistenceException if the query fails.
+         * @throws PersistenceException if the single row's value is null, or the query fails.
          */
         get() {
             resultStream.use { stream ->
-                return stream
-                    .reduce { _, _ ->
-                        throw NonUniqueResultException("Expected single result, but found more than one.")
-                    }
-                    .orElseThrow(Supplier { NoResultException("Expected single result, but found none.") })
+                val iterator = stream.iterator()
+                if (!iterator.hasNext()) {
+                    throw NoResultException("Expected single result, but found none.")
+                }
+                val result = iterator.next()
+                if (iterator.hasNext()) {
+                    throw NonUniqueResultException("Expected single result, but found more than one.")
+                }
+                if (result == null) {
+                    throw PersistenceException("Expected single result, but found null. Wrap the field in COALESCE() to provide a non-null default.")
+                }
+                return result
             }
         }
 
@@ -1031,16 +1037,24 @@ interface QueryBuilder<T : Data, R, ID> {
         /**
          * Executes the query and returns an optional result.
          *
-         * @return the optional result.
+         * @return the optional result; `null` when no row matched.
          * @throws NonUniqueResultException if more than one result.
-         * @throws PersistenceException if the query fails.
+         * @throws PersistenceException if the single row's value is null, or the query fails.
          */
         get() {
             resultStream.use { stream ->
-                return stream.reduce { _, _ ->
+                val iterator = stream.iterator()
+                if (!iterator.hasNext()) {
+                    return null
+                }
+                val result = iterator.next()
+                if (iterator.hasNext()) {
                     throw NonUniqueResultException("Expected single result, but found more than one.")
                 }
-                    .orElse(null)
+                if (result == null) {
+                    throw PersistenceException("Result is null. Wrap the field in COALESCE() to provide a non-null default.")
+                }
+                return result
             }
         }