diff --git a/src/java/org/apache/sqoop/mapreduce/MergeMapperBase.java b/src/java/org/apache/sqoop/mapreduce/MergeMapperBase.java
index 4657e0a0..216fcd05 100644
--- a/src/java/org/apache/sqoop/mapreduce/MergeMapperBase.java
+++ b/src/java/org/apache/sqoop/mapreduce/MergeMapperBase.java
@@ -74,7 +74,18 @@ protected void processRecord(SqoopRecord r, Context c)
     if (null == fieldMap) {
       throw new IOException("No field map in record " + r);
     }
-    Object keyObj = fieldMap.get(keyColName);
+    Object keyObj = null;
+    if (keyColName.contains(",")) {
+        String connectStr = new String(new byte[]{1});
+        StringBuilder keyFieldsSb = new StringBuilder();
+        for (String str : keyColName.split(",")) {
+            keyFieldsSb.append(connectStr).append(fieldMap.get(str).toString());
+        }
+        keyObj = keyFieldsSb;
+    } else {
+        keyObj = fieldMap.get(keyColName);
+    }
+
     if (null == keyObj) {
       throw new IOException("Cannot join values on null key. "
           + "Did you specify a key column that exists?");