diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingResultSetMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingResultSetMapper.java
index 98ce9b5..a48a900 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingResultSetMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingResultSetMapper.java
@@ -132,7 +132,7 @@ public class CachingResultSetMapper extends ResultSetMapper {
 	}
 
 	@Override
-	protected <T> RowToObjectMapper<T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		return new CachingRowToObjectMapper<T>(cache, resultSet, returnTypeClass, cal, mapValType);
+	protected <K, T> RowToObjectMapper<K, T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		return new CachingRowToObjectMapper<K, T>(cache, resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 	}
 }
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingRowToObjectMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingRowToObjectMapper.java
index fb3b61d..579036c 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingRowToObjectMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CachingRowToObjectMapper.java
@@ -11,18 +11,18 @@ import java.util.Map;
 /**
  * Maps same as RowToObjectMapper except caches constructor and field mappings
  */
-public class CachingRowToObjectMapper<T> extends RowToObjectMapper<T> {
+public class CachingRowToObjectMapper<K, T> extends RowToObjectMapper<K, T> {
 
 	protected final Map<ResultSetKey, FieldMapping<T>> cache;
 	protected final ResultSetKey keys;
 
-	public CachingRowToObjectMapper(final Map<ResultSetKey, FieldMapping<?>> cache, ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		super(resultSet, returnTypeClass, cal, mapValType);
+	public CachingRowToObjectMapper(final Map<ResultSetKey, FieldMapping<?>> cache, ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		super(resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 		@SuppressWarnings("unchecked")
 		final Map<ResultSetKey, FieldMapping<T>> genericCache = (Map<ResultSetKey, FieldMapping<T>>) (Object) cache; // ridiculous ain't it?
 		this.cache = genericCache;
 		try {
-			keys = new ResultSetKey(super.getKeysFromResultSet(), _returnTypeClass);
+			keys = new ResultSetKey(super.getKeysFromResultSet(), _returnTypeClass, _mapKeyType);
 			//System.out.printf("keys: %s\n", keys);
 		} catch (SQLException e) {
 			throw new MapperException("CachingRowToObjectMapper: SQLException: " + e.getMessage(), e);
@@ -55,11 +55,12 @@ public class CachingRowToObjectMapper<T> extends RowToObjectMapper<T> {
 
 	public static class ResultSetKey {
 		protected final String[] keys;
-		protected final Class<?> returnTypeClass;
+		protected final Class<?> returnTypeClass, mapKeyType;
 
-		public ResultSetKey(final String[] keys, final Class<?> returnTypeClass) {
+		public ResultSetKey(final String[] keys, final Class<?> returnTypeClass, final Class<?> mapKeyType) {
 			this.keys = keys;
 			this.returnTypeClass = returnTypeClass;
+			this.mapKeyType = mapKeyType;
 		}
 
 		@Override
@@ -69,13 +70,18 @@ public class CachingRowToObjectMapper<T> extends RowToObjectMapper<T> {
 
 			final ResultSetKey that = (ResultSetKey) o;
 
-			return Arrays.equals(keys, that.keys) && (returnTypeClass != null ? returnTypeClass.equals(that.returnTypeClass) : that.returnTypeClass == null);
+			// Probably incorrect - comparing Object[] arrays with Arrays.equals
+			if (!Arrays.equals(keys, that.keys)) return false;
+			if (returnTypeClass != null ? !returnTypeClass.equals(that.returnTypeClass) : that.returnTypeClass != null)
+				return false;
+			return mapKeyType != null ? mapKeyType.equals(that.mapKeyType) : that.mapKeyType == null;
 		}
 
 		@Override
 		public int hashCode() {
 			int result = Arrays.hashCode(keys);
 			result = 31 * result + (returnTypeClass != null ? returnTypeClass.hashCode() : 0);
+			result = 31 * result + (mapKeyType != null ? mapKeyType.hashCode() : 0);
 			return result;
 		}
 
@@ -84,6 +90,7 @@ public class CachingRowToObjectMapper<T> extends RowToObjectMapper<T> {
 			return "ResultSetKey{" +
 					"keys=" + Arrays.toString(keys) +
 					", returnTypeClass=" + returnTypeClass +
+					", mapKeyType=" + mapKeyType +
 					'}';
 		}
 	}
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapResultSetMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapResultSetMapper.java
index 8f1cc25..e2b57be 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapResultSetMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapResultSetMapper.java
@@ -15,7 +15,7 @@ public class CaseInsensitiveMapResultSetMapper extends ResultSetMapper {
 	}
 
 	@Override
-	protected <T> RowToObjectMapper<T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		return new CaseInsensitiveMapRowToObjectMapper<T>(resultSet, returnTypeClass, cal, mapValType);
+	protected <K, T> RowToObjectMapper<K, T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		return new CaseInsensitiveMapRowToObjectMapper<K, T>(resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 	}
 }
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapRowToObjectMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapRowToObjectMapper.java
index 3ac31b9..bbe8242 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapRowToObjectMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CaseInsensitiveMapRowToObjectMapper.java
@@ -8,7 +8,7 @@ import java.util.Map;
 /**
  * Created by mopar on 5/15/14.
  */
-public class CaseInsensitiveMapRowToObjectMapper<T> extends RowToObjectMapper<T> {
+public class CaseInsensitiveMapRowToObjectMapper<K, T> extends RowToObjectMapper<K, T> {
 	public CaseInsensitiveMapRowToObjectMapper(ResultSet resultSet, Class<T> returnTypeClass) {
 		super(resultSet, returnTypeClass);
 	}
@@ -25,6 +25,10 @@ public class CaseInsensitiveMapRowToObjectMapper<T> extends RowToObjectMapper<T>
 		super(resultSet, returnTypeClass, cal, mapValType);
 	}
 
+	public CaseInsensitiveMapRowToObjectMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		super(resultSet, returnTypeClass, cal, mapValType, mapKeyType);
+	}
+
 	@Override
 	protected Map<String, Object> getMapImplementation() throws IllegalAccessException, InstantiationException {
 		if(HashMap.class.equals(_returnTypeClass))
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningResultSetMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningResultSetMapper.java
index 14f77eb..5139003 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningResultSetMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningResultSetMapper.java
@@ -19,7 +19,7 @@ public class CleaningResultSetMapper<E> extends ResultSetMapper {
 
 	@Override
 	@SuppressWarnings({"unchecked"})
-	protected <T> RowToObjectMapper<T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		return new CleaningRowToObjectMapper<T>((Cleaner<T>)cleaner, resultSet, returnTypeClass, cal, mapValType);
+	protected <K, T> RowToObjectMapper<K, T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		return new CleaningRowToObjectMapper<K, T>((Cleaner<T>)cleaner, resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 	}
 }
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningRowToObjectMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningRowToObjectMapper.java
index 91d3388..bfe7ea9 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningRowToObjectMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CleaningRowToObjectMapper.java
@@ -1,21 +1,22 @@
 package com.moparisthebest.jdbc;
 
 import java.sql.ResultSet;
+import java.sql.SQLException;
 import java.util.Calendar;
 
-public class CleaningRowToObjectMapper<T> extends RowToObjectMapper<T> {
+public class CleaningRowToObjectMapper<K, T> extends RowToObjectMapper<K, T> {
 
 	private final Cleaner<T> cleaner;
 
-	public CleaningRowToObjectMapper(Cleaner<T> cleaner, ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		super(resultSet, returnTypeClass, cal, mapValType);
+	public CleaningRowToObjectMapper(Cleaner<T> cleaner, ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		super(resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 		if (cleaner == null)
 			throw new NullPointerException("cleaner cannot be null!");
 		this.cleaner = cleaner;
 	}
 
 	@Override
-	public T mapRowToReturnType() {
+	public T mapRowToReturnType() throws SQLException {
 		return cleaner.clean(super.mapRowToReturnType());
 	}
 }
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingResultSetMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingResultSetMapper.java
index 30a2df2..3ef4c0b 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingResultSetMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingResultSetMapper.java
@@ -25,7 +25,7 @@ import java.util.concurrent.ConcurrentHashMap;
 public class CompilingResultSetMapper extends ResultSetMapper {
 
 	protected final Compiler compiler = new Compiler();
-	protected final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>> cache;
+	protected final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>> cache;
 
 	/**
 	 * CompilingResultSetMapper with optional maxEntries, expiring old ones in LRU fashion
@@ -40,14 +40,14 @@ public class CompilingResultSetMapper extends ResultSetMapper {
 			final float loadFactor = 0.75f; // default for HashMaps
 			// if we set the initialCapacity this way, nothing should ever need re-sized
 			final int initialCapacity = ((int) Math.ceil(maxEntries / loadFactor)) + 1;
-			cache = new LinkedHashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>>(initialCapacity, loadFactor, true) {
+			cache = new LinkedHashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>>(initialCapacity, loadFactor, true) {
 				@Override
-				protected boolean removeEldestEntry(final Map.Entry<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>> eldest) {
+				protected boolean removeEldestEntry(final Map.Entry<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>> eldest) {
 					return size() > maxEntries;
 				}
 			};
 		} else
-			cache = new HashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>>();
+			cache = new HashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>>();
 	}
 
 	/**
@@ -83,7 +83,7 @@ public class CompilingResultSetMapper extends ResultSetMapper {
 	 * @param arrayMaxLength max array/list/map length, a value of less than 1 indicates that all rows from the ResultSet should be included
 	 * @param cache          any Map implementation for cache you wish, does not need to handle null keys or values
 	 */
-	public CompilingResultSetMapper(final Calendar cal, final int arrayMaxLength, final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>> cache) {
+	public CompilingResultSetMapper(final Calendar cal, final int arrayMaxLength, final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>> cache) {
 		super(cal, arrayMaxLength);
 		if (cache == null)
 			throw new IllegalArgumentException("cache cannot be null");
@@ -96,7 +96,7 @@ public class CompilingResultSetMapper extends ResultSetMapper {
 	 * @param arrayMaxLength max array/list/map length, a value of less than 1 indicates that all rows from the ResultSet should be included
 	 * @param cache          any Map implementation for cache you wish, does not need to handle null keys or values
 	 */
-	public CompilingResultSetMapper(final int arrayMaxLength, final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>> cache) {
+	public CompilingResultSetMapper(final int arrayMaxLength, final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>> cache) {
 		this(null, arrayMaxLength, cache);
 	}
 
@@ -105,7 +105,7 @@ public class CompilingResultSetMapper extends ResultSetMapper {
 	 *
 	 * @param cache any Map implementation for cache you wish, does not need to handle null keys or values
 	 */
-	public CompilingResultSetMapper(final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>> cache) {
+	public CompilingResultSetMapper(final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>> cache) {
 		this(-1, cache);
 	}
 
@@ -118,9 +118,9 @@ public class CompilingResultSetMapper extends ResultSetMapper {
 	 */
 	public CompilingResultSetMapper(final Calendar cal, final int arrayMaxLength, final boolean threadSafe) {
 		this(cal, arrayMaxLength, threadSafe ?
-				new ConcurrentHashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>>()
+				new ConcurrentHashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>>()
 				:
-				new HashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>>()
+				new HashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>>()
 		);
 	}
 
@@ -144,7 +144,7 @@ public class CompilingResultSetMapper extends ResultSetMapper {
 	}
 
 	@Override
-	protected <T> RowToObjectMapper<T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		return new CompilingRowToObjectMapper<T>(compiler, cache, resultSet, returnTypeClass, cal, mapValType);
+	protected <K, T> RowToObjectMapper<K, T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		return new CompilingRowToObjectMapper<K, T>(compiler, cache, resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 	}
 }
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingRowToObjectMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingRowToObjectMapper.java
index 2d360dd..879a534 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingRowToObjectMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/CompilingRowToObjectMapper.java
@@ -26,20 +26,23 @@ import java.util.Map;
  * 1. Normally a subclass of RowToObjectMapper can overload the getMapImplementation() method to change some behavior,
  * @see CaseInsensitiveMapRowToObjectMapper , but that method is never called with this implementation.
  */
-public class CompilingRowToObjectMapper<T> extends RowToObjectMapper<T> {
+public class CompilingRowToObjectMapper<K, T> extends RowToObjectMapper<K, T> {
+
+	public static final String firstColumnError = "Cannot call getFirstColumn when mapKeyType is null!";
+
 	protected final Compiler compiler;
-	protected final ResultSetToObject<T> resultSetToObject;
+	protected final ResultSetToObject<K, T> resultSetToObject;
 
 	protected String[] keys = null; // for caching if we must generate class
 
-	public CompilingRowToObjectMapper(final Compiler compiler, final Map<CachingRowToObjectMapper.ResultSetKey, ResultSetToObject<?>> cache, ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		super(resultSet, returnTypeClass, cal, mapValType);
+	public CompilingRowToObjectMapper(final Compiler compiler, final Map<CachingRowToObjectMapper.ResultSetKey, ResultSetToObject<?,?>> cache, ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		super(resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 		this.compiler = compiler;
 		try {
-			final CachingRowToObjectMapper.ResultSetKey keys = new CachingRowToObjectMapper.ResultSetKey(super.getKeysFromResultSet(), _returnTypeClass);
+			final CachingRowToObjectMapper.ResultSetKey keys = new CachingRowToObjectMapper.ResultSetKey(super.getKeysFromResultSet(), _returnTypeClass, _mapKeyType);
 			//System.out.printf("keys: %s\n", keys);
 			@SuppressWarnings("unchecked")
-			final ResultSetToObject<T> resultSetToObject = (ResultSetToObject<T>) cache.get(keys);
+			final ResultSetToObject<K,T> resultSetToObject = (ResultSetToObject<K,T>) cache.get(keys);
 			if (resultSetToObject == null) {
 				//System.out.printf("cache miss, keys: %s\n", keys);
 				// generate and put into cache
@@ -60,15 +63,15 @@ public class CompilingRowToObjectMapper<T> extends RowToObjectMapper<T> {
 	}
 
 	@Override
-	public T mapRowToReturnType() {
-		try {
-			return resultSetToObject.toObject(_resultSet, _cal);
-		} catch (SQLException e) {
-			throw new MapperException(e.getMessage(), e);
-		}
+	public T mapRowToReturnType() throws SQLException {
+		return resultSetToObject.toObject(_resultSet, _cal);
 	}
 
-	// todo: generate/cache these to make it faster for Map and MapCollection? maybe just getKey and getVal methods instead
+	@Override
+	public K getMapKey() throws SQLException {
+		return resultSetToObject.getFirstColumn(_resultSet, _cal);
+	}
+// todo: generate/cache these to make it faster for Map and MapCollection? maybe just getKey and getVal methods instead
 	/*
 	@Override
 	public <E> E extractColumnValue(final int index, final Class<E> classType) throws SQLException {
@@ -88,11 +91,14 @@ public class CompilingRowToObjectMapper<T> extends RowToObjectMapper<T> {
 		throw new MapperException("not supported here");
 	}
 
-	public interface ResultSetToObject<T> {
+	public interface ResultSetToObject<K, T> {
+		K getFirstColumn(final ResultSet rs, final Calendar cal) throws SQLException;
 		T toObject(final ResultSet rs, final Calendar cal) throws SQLException;
 	}
 
 	protected String typeFromName(final Class<?> type) {
+		if(type == null)
+			return "Object";
 		if(_columnCount == 1 && type.isPrimitive()) {
 			// need the object equivalent here, what is the best way? this works, isn't pretty...
 			if(type.equals(Character.TYPE))
@@ -141,27 +147,44 @@ public class CompilingRowToObjectMapper<T> extends RowToObjectMapper<T> {
 	}
 
 	// code generation down here
-	protected ResultSetToObject<T> genClass() {
+	protected ResultSetToObject<K, T> genClass() {
 		final String className = "CompilingMapper";
 		final String tType = typeFromName(_returnTypeClass);
+		final String kType = typeFromName(_mapKeyType);
 		final String header =
 				"import static com.moparisthebest.jdbc.util.ResultSetUtil.*;\n\n" +
 						"public final class " + className +
-						" implements com.moparisthebest.jdbc.CompilingRowToObjectMapper.ResultSetToObject<" + tType + "> {\n" +
+						" implements com.moparisthebest.jdbc.CompilingRowToObjectMapper.ResultSetToObject<"+ kType +"," + tType + "> {\n" +
 						"  public " + tType + " toObject(final java.sql.ResultSet rs, final java.util.Calendar cal) throws java.sql.SQLException {\n";
-		final String footer = "  }\n" +
+		final String footer = ";\n  }\n" +
 				"}\n";
 
 		final StringBuilder java = new StringBuilder(header);
 		//java.append("return null;\n");
 		gen(java, tType);
+
+		java.append("  }\n\n  public ").append(kType).append(" getFirstColumn(final java.sql.ResultSet rs, final java.util.Calendar cal) throws java.sql.SQLException {\n    ");
+		if(_mapKeyType != null){
+			java.append("return ");
+			extractColumnValueString(java, 1, _tmf.getTypeId(_mapKeyType));
+		} else {
+			java.append("throw new com.moparisthebest.jdbc.MapperException(com.moparisthebest.jdbc.CompilingRowToObjectMapper.firstColumnError)");
+		}
+
 		java.append(footer);
-		//System.out.println(java);
+		System.out.println(java);
 		return compiler.compile(className, java);
 	}
 
 	protected void gen(final StringBuilder java, final String tType) {
 
+		if(mapOnlySecondColumn){
+			java.append("return ");
+			extractColumnValueString(java, 2, _tmf.getTypeId(_returnTypeClass));
+			java.append(";\n");
+			return;
+		}
+
 		lazyLoadConstructor();
 
 		if (resultSetConstructor) {
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/ResultSetMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/ResultSetMapper.java
index 45c3ec1..7bae004 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/ResultSetMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/ResultSetMapper.java
@@ -120,7 +120,7 @@ public class ResultSetMapper {
 		T ret = null;
 		try {
 			if (rs.next())
-				ret = getRowMapper(rs, componentType, cal, mapValType).mapRowToReturnType();
+				ret = getRowMapper(rs, componentType, cal, mapValType, null).mapRowToReturnType();
 		} catch (SQLException e) {
 			// ignore
 		}
@@ -151,7 +151,7 @@ public class ResultSetMapper {
 			// a value of less than 1 indicates that all rows from the ResultSet should be included.
 			final boolean unlimitedRows = arrayMaxLength < 1;
 
-			final RowToObjectMapper<E> rowMapper = getRowMapper(rs, componentType, cal, mapValType);
+			final RowToObjectMapper<?, E> rowMapper = getRowMapper(rs, componentType, cal, mapValType, null);
 
 			for (; (unlimitedRows || numRows != arrayMaxLength) && rs.next(); ++numRows) {
 				E object = rowMapper.mapRowToReturnType();
@@ -230,12 +230,11 @@ public class ResultSetMapper {
 			// a value of less than 1 indicates that all rows from the ResultSet should be included.
 			final boolean unlimitedRows = arrayMaxLength < 1;
 
-			final RowToObjectMapper<E> rowMapper = getRowMapper(rs, componentType, cal, mapValType);
+			final RowToObjectMapper<K, E> rowMapper = getRowMapper(rs, componentType, cal, mapValType, mapKeyType);
 
-			boolean onlyTwoColumns = rowMapper.getColumnCount() == 2;
 			for (; (unlimitedRows || numRows != arrayMaxLength) && rs.next(); ++numRows) {
-				K key = rowMapper.extractColumnValue(1, mapKeyType);
-				E value = onlyTwoColumns ? rowMapper.extractColumnValue(2, componentType) : rowMapper.mapRowToReturnType();
+				K key = rowMapper.getMapKey();
+				E value = rowMapper.mapRowToReturnType();
 
 				map = softMap.get();
 				if (map == null)
@@ -312,12 +311,11 @@ public class ResultSetMapper {
 			// a value of less than 1 indicates that all rows from the ResultSet should be included.
 			final boolean unlimitedRows = arrayMaxLength < 1;
 
-			final RowToObjectMapper<C> rowMapper = getRowMapper(rs, componentType, cal, mapValType);
+			final RowToObjectMapper<K, C> rowMapper = getRowMapper(rs, componentType, cal, mapValType, mapKeyType);
 
-			boolean onlyTwoColumns = rowMapper.getColumnCount() == 2;
 			for (; (unlimitedRows || numRows != arrayMaxLength) && rs.next(); ++numRows) {
-				K key = rowMapper.extractColumnValue(1, mapKeyType);
-				C value = onlyTwoColumns ? rowMapper.extractColumnValue(2, componentType) : rowMapper.mapRowToReturnType();
+				K key = rowMapper.getMapKey();
+				C value = rowMapper.mapRowToReturnType();
 
 				map = softMap.get();
 				if (map == null)
@@ -406,8 +404,8 @@ public class ResultSetMapper {
 	}
 
 	// fairly un-interesting methods below here
-	protected <T> RowToObjectMapper<T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		return new RowToObjectMapper<T>(resultSet, returnTypeClass, cal, mapValType);
+	protected <K, T> RowToObjectMapper<K, T> getRowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		return new RowToObjectMapper<K, T>(resultSet, returnTypeClass, cal, mapValType, mapKeyType);
 	}
 
 	protected void warnOnMaxLength(final int numRows, final int arrayMaxLength, final ResultSet rs) {
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowMapper.java
index f9dc5e3..de4dd89 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowMapper.java
@@ -37,7 +37,7 @@ import java.util.regex.Pattern;
  * RowMapperFactory.
  *
  */
-public abstract class RowMapper {
+public abstract class RowMapper<K, T> {
 
     private static final String SETTER_NAME_REGEX = "^(set)([A-Z_]\\w*+)";
     protected static final TypeMappingsFactory _tmf = TypeMappingsFactory.getInstance();
@@ -50,34 +50,51 @@ public abstract class RowMapper {
     protected final Calendar _cal;
 
     /** Class to map ResultSet Rows to. */
-    protected final Class<?> _returnTypeClass;
+    protected final Class<T> _returnTypeClass;
+
+    protected final Class<K> _mapKeyType;
 
     protected final int _columnCount;
 
+    protected final boolean mapOnlySecondColumn;
+
     /**
      * Create a new RowMapper for the specified ResultSet and return type Class.
      * @param resultSet ResultSet to map
      * @param returnTypeClass Class to map ResultSet rows to.
      * @param cal Calendar instance for date/time values.
      */
-    protected RowMapper(ResultSet resultSet, Class<?> returnTypeClass, Calendar cal) {
+    protected RowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<K> mapKeyType) {
         _resultSet = resultSet;
         _returnTypeClass = returnTypeClass;
         _cal = cal;
+        _mapKeyType = mapKeyType;
 
         try {
             _columnCount = resultSet.getMetaData().getColumnCount();
         } catch (SQLException e) {
             throw new MapperException("RowToObjectMapper: SQLException: " + e.getMessage(), e);
         }
+
+        mapOnlySecondColumn = _mapKeyType != null && _columnCount == 2;
+    }
+
+    protected RowMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal) {
+        this(resultSet, returnTypeClass, cal, null);
     }
 
     /**
      * Map a ResultSet row to the return type class
-     * @return An instance of class.
+     * @return An instance of class, if _mapKeyType is not null and _columnCount is 2, return only index 2
      */
-    public abstract Object mapRowToReturnType();
+    public abstract T mapRowToReturnType() throws SQLException;
 
+    /**
+     * key for map
+     * @return index number 1, with type of _mapKeyType
+     * @throws MapperException if _mapKeyType is null
+     */
+    public abstract K getMapKey() throws SQLException;
 
     /**
      * Build a String array of column names from the ResultSet.
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowToObjectMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowToObjectMapper.java
index 79325d0..b3bd4a2 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowToObjectMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/RowToObjectMapper.java
@@ -47,7 +47,7 @@ import static com.moparisthebest.jdbc.UpdateableDTO.NO;
  *
  * @author Travis Burtrum (modifications from beehive)
  */
-public class RowToObjectMapper<T> extends RowMapper {
+public class RowToObjectMapper<K, T> extends RowMapper<K, T> {
 
 	public static final int TYPE_BOOLEAN = _tmf.getTypeId(Boolean.TYPE);//TypeMappingsFactory.TYPE_BOOLEAN; // not public? 
 	public static final int TYPE_BOOLEAN_OBJ = _tmf.getTypeId(Boolean.class);//TypeMappingsFactory.TYPE_BOOLEAN_OBJ; // not public?
@@ -77,6 +77,11 @@ public class RowToObjectMapper<T> extends RowMapper {
 		this(resultSet, returnTypeClass, cal, null);
 	}
 
+
+	public RowToObjectMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
+		this(resultSet, returnTypeClass, cal, mapValType, null);
+	}
+
 	/**
 	 * Create a new RowToObjectMapper.
 	 *
@@ -84,8 +89,8 @@ public class RowToObjectMapper<T> extends RowMapper {
 	 * @param returnTypeClass Class to map to.
 	 * @param cal             Calendar instance for date/time mappings.
 	 */
-	public RowToObjectMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType) {
-		super(resultSet, returnTypeClass, cal);
+	public RowToObjectMapper(ResultSet resultSet, Class<T> returnTypeClass, Calendar cal, Class<?> mapValType, Class<K> mapKeyType) {
+		super(resultSet, returnTypeClass, cal, mapKeyType);
 		returnMap = Map.class.isAssignableFrom(returnTypeClass);
 		if(returnMap){
 			_returnTypeClass = ResultSetMapper.getConcreteClass(returnTypeClass, HashMap.class);
@@ -136,13 +141,21 @@ public class RowToObjectMapper<T> extends RowMapper {
 		return (Map<String, Object>)_returnTypeClass.newInstance();
 	}
 
+	@Override
+	public K getMapKey() throws SQLException {
+		return this.extractColumnValue(1, _mapKeyType);
+	}
+
 	/**
 	 * Do the mapping.
 	 *
 	 * @return An object instance.
 	 */
 	@SuppressWarnings({"unchecked"})
-	public T mapRowToReturnType() {
+	public T mapRowToReturnType() throws SQLException {
+
+		if(mapOnlySecondColumn)
+			return this.extractColumnValue(2, _returnTypeClass);
 
 		lazyLoadConstructor();
 
@@ -300,15 +313,6 @@ public class RowToObjectMapper<T> extends RowMapper {
 			return classType.cast(extractColumnValue(index, _tmf.getTypeId(classType)));
 	}
 
-	/**
-	 * Provided so we know whether to map all values to a type, or just the second one
-	 *
-	 * @return
-	 */
-	public int getColumnCount() {
-		return this._columnCount;
-	}
-
 	/**
 	 * Build the structures necessary to do the mapping
 	 *
diff --git a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/StaticCompilingResultSetMapper.java b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/StaticCompilingResultSetMapper.java
index 1ec61b7..c2a2f31 100644
--- a/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/StaticCompilingResultSetMapper.java
+++ b/beehive-jdbc-mapper/src/main/java/com/moparisthebest/jdbc/StaticCompilingResultSetMapper.java
@@ -9,7 +9,7 @@ import java.util.concurrent.ConcurrentHashMap;
  */
 public class StaticCompilingResultSetMapper extends CompilingResultSetMapper {
 
-	private static final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>> cache = new ConcurrentHashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?>>();
+	private static final Map<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>> cache = new ConcurrentHashMap<CachingRowToObjectMapper.ResultSetKey, CompilingRowToObjectMapper.ResultSetToObject<?,?>>();
 
 	public static final StaticCompilingResultSetMapper instance = new StaticCompilingResultSetMapper();