diff --git a/mysql-test/r/join.result b/mysql-test/r/join.result
index baabf48cb2f..8691eb27220 100644
--- a/mysql-test/r/join.result
+++ b/mysql-test/r/join.result
@@ -1128,3 +1128,20 @@ EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 DROP VIEW v1;
 DROP TABLE t1, t2;
+CREATE TABLE t1(a CHAR(9),b INT,KEY(b),KEY(a)) ENGINE=MYISAM;
+CREATE TABLE t2(a CHAR(9),b INT,KEY(b),KEY(a)) ENGINE=MYISAM;
+INSERT INTO t1 VALUES ('1',null),(null,null);
+INSERT INTO t2 VALUES ('1',null),(null,null);
+CREATE TABLE mm1(a CHAR(9),b INT,KEY(b),KEY(a))
+ENGINE=MERGE  UNION=(t1,t2);
+SELECT t1.a FROM mm1,t1;
+a
+NULL
+1
+NULL
+1
+NULL
+1
+NULL
+1
+DROP TABLE t1, t2, mm1;
diff --git a/mysql-test/t/join.test b/mysql-test/t/join.test
index dbf36dedec8..645321a3a5e 100644
--- a/mysql-test/t/join.test
+++ b/mysql-test/t/join.test
@@ -804,3 +804,15 @@ DEALLOCATE PREPARE stmt;
 
 DROP VIEW v1;
 DROP TABLE t1, t2;
+
+#
+# Bug#45195 valgrind warnings about uninitialized values in store_record_in_cache()
+#
+CREATE TABLE t1(a CHAR(9),b INT,KEY(b),KEY(a)) ENGINE=MYISAM;
+CREATE TABLE t2(a CHAR(9),b INT,KEY(b),KEY(a)) ENGINE=MYISAM;
+INSERT INTO t1 VALUES ('1',null),(null,null);
+INSERT INTO t2 VALUES ('1',null),(null,null);
+CREATE TABLE mm1(a CHAR(9),b INT,KEY(b),KEY(a))
+ENGINE=MERGE  UNION=(t1,t2);
+SELECT t1.a FROM mm1,t1;
+DROP TABLE t1, t2, mm1;
diff --git a/sql/field.cc b/sql/field.cc
index d8db3fdbae4..15ee9c4a86c 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -1705,11 +1705,10 @@ uint Field::fill_cache_field(CACHE_FIELD *copy)
   uint store_length;
   copy->str=ptr;
   copy->length=pack_length();
-  copy->blob_field=0;
+  copy->field= this;
   if (flags & BLOB_FLAG)
   {
-    copy->blob_field=(Field_blob*) this;
-    copy->strip=0;
+    copy->type= CACHE_BLOB;
     copy->length-= table->s->blob_ptr_size;
     return copy->length;
   }
@@ -1717,15 +1716,15 @@ uint Field::fill_cache_field(CACHE_FIELD *copy)
            (type() == MYSQL_TYPE_STRING && copy->length >= 4 &&
             copy->length < 256))
   {
-    copy->strip=1;				/* Remove end space */
+    copy->type= CACHE_STRIPPED;
     store_length= 2;
   }
   else
   {
-    copy->strip=0;
+    copy->type= 0;
     store_length= 0;
   }
-  return copy->length+ store_length;
+  return copy->length + store_length;
 }
 
 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index b1efaf67b9b..a3ce50fe4ee 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -14149,7 +14149,7 @@ join_init_cache(THD *thd,JOIN_TAB *tables,uint table_count)
       {
 	used_fields--;
 	length+=field->fill_cache_field(copy);
-	if (copy->blob_field)
+	if (copy->type == CACHE_BLOB)
 	  (*blob_ptr++)=copy;
 	if (field->real_maybe_null())
 	  null_fields++;
@@ -14164,8 +14164,8 @@ join_init_cache(THD *thd,JOIN_TAB *tables,uint table_count)
     {						/* must copy null bits */
       copy->str= tables[i].table->null_flags;
       copy->length= tables[i].table->s->null_bytes;
-      copy->strip=0;
-      copy->blob_field=0;
+      copy->type=0;
+      copy->field=0;
       length+=copy->length;
       copy++;
       cache->fields++;
@@ -14175,8 +14175,8 @@ join_init_cache(THD *thd,JOIN_TAB *tables,uint table_count)
     {
       copy->str= (uchar*) &tables[i].table->null_row;
       copy->length=sizeof(tables[i].table->null_row);
-      copy->strip=0;
-      copy->blob_field=0;
+      copy->type=0;
+      copy->field=0;
       length+=copy->length;
       copy++;
       cache->fields++;
@@ -14201,9 +14201,10 @@ used_blob_length(CACHE_FIELD **ptr)
   uint length,blob_length;
   for (length=0 ; *ptr ; ptr++)
   {
-    (*ptr)->blob_length=blob_length=(*ptr)->blob_field->get_length();
+    Field_blob *field_blob= (Field_blob *) (*ptr)->field;
+    (*ptr)->blob_length=blob_length= field_blob->get_length();
     length+=blob_length;
-    (*ptr)->blob_field->get_ptr(&(*ptr)->str);
+    field_blob->get_ptr(&(*ptr)->str);
   }
   return length;
 }
@@ -14232,30 +14233,35 @@ store_record_in_cache(JOIN_CACHE *cache)
   cache->records++;
   for (copy=cache->field ; copy < end_field; copy++)
   {
-    if (copy->blob_field)
+    if (copy->type == CACHE_BLOB)
     {
+      Field_blob *blob_field= (Field_blob *) copy->field;
       if (last_record)
       {
-	copy->blob_field->get_image(pos, copy->length+sizeof(char*), 
-				    copy->blob_field->charset());
+	blob_field->get_image(pos, copy->length+sizeof(char*), 
+                              blob_field->charset());
 	pos+=copy->length+sizeof(char*);
       }
       else
       {
-	copy->blob_field->get_image(pos, copy->length, // blob length
-				    copy->blob_field->charset());
+	blob_field->get_image(pos, copy->length, // blob length
+                              blob_field->charset());
 	memcpy(pos+copy->length,copy->str,copy->blob_length);  // Blob data
 	pos+=copy->length+copy->blob_length;
       }
     }
     else
     {
-      if (copy->strip)
+      if (copy->type == CACHE_STRIPPED)
       {
 	uchar *str,*end;
-	for (str=copy->str,end= str+copy->length;
-	     end > str && end[-1] == ' ' ;
-	     end--) ;
+        Field *field= copy->field;
+        if (field && field->maybe_null() && field->is_null())
+          end= str= copy->str;
+        else
+          for (str=copy->str,end= str+copy->length;
+               end > str && end[-1] == ' ' ;
+               end--) ;
 	length=(uint) (end-str);
 	memcpy(pos+2, str, length);
         int2store(pos, length);
@@ -14304,23 +14310,24 @@ read_cached_record(JOIN_TAB *tab)
        copy < end_field;
        copy++)
   {
-    if (copy->blob_field)
+    if (copy->type == CACHE_BLOB)
     {
+      Field_blob *blob_field= (Field_blob *) copy->field;
       if (last_record)
       {
-	copy->blob_field->set_image(pos, copy->length+sizeof(char*),
-				    copy->blob_field->charset());
+	blob_field->set_image(pos, copy->length+sizeof(char*),
+                              blob_field->charset());
 	pos+=copy->length+sizeof(char*);
       }
       else
       {
-	copy->blob_field->set_ptr(pos, pos+copy->length);
-	pos+=copy->length+copy->blob_field->get_length();
+	blob_field->set_ptr(pos, pos+copy->length);
+	pos+=copy->length + blob_field->get_length();
       }
     }
     else
     {
-      if (copy->strip)
+      if (copy->type == CACHE_STRIPPED)
       {
         length= uint2korr(pos);
 	memcpy(copy->str, pos+2, length);
diff --git a/sql/sql_select.h b/sql/sql_select.h
index bfff0a0ffa2..ef43f9b049c 100644
--- a/sql/sql_select.h
+++ b/sql/sql_select.h
@@ -95,6 +95,10 @@ typedef struct st_table_ref
 } TABLE_REF;
 
 
+
+#define CACHE_BLOB      1        /* blob field  */
+#define CACHE_STRIPPED  2        /* field stripped of trailing spaces */
+
 /**
   CACHE_FIELD and JOIN_CACHE is used on full join to cache records in outer
   table
@@ -103,8 +107,8 @@ typedef struct st_table_ref
 typedef struct st_cache_field {
   uchar *str;
   uint length, blob_length;
-  Field_blob *blob_field;
-  bool strip;
+  Field *field;
+  uint type;    /**< category of the of the copied field (CACHE_BLOB et al.) */
 } CACHE_FIELD;