diff --git a/src/main/java/fr/pandacube/util/orm/ORM.java b/src/main/java/fr/pandacube/util/orm/ORM.java
index 2aa8384..a4edcd0 100644
--- a/src/main/java/fr/pandacube/util/orm/ORM.java
+++ b/src/main/java/fr/pandacube/util/orm/ORM.java
@@ -5,6 +5,7 @@ import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
@@ -14,7 +15,6 @@ import java.util.function.Consumer;
 import org.javatuples.Pair;
 
 import fr.pandacube.util.Log;
-import fr.pandacube.util.orm.SQLWhereComp.SQLComparator;
 
 /**
  * <b>ORM = Object-Relational Mapping</b>
@@ -102,39 +102,35 @@ public final class ORM {
 		return (SQLField<E, Integer>) SQLElement.fieldsCache.get(elemClass).get("id");
 	}
 
-	public static <E extends SQLElement<E>> SQLElementList<E> getByIds(Class<E> elemClass, Collection<Integer> ids)
-			throws ORMException {
-		return getByIds(elemClass, ids.toArray(new Integer[ids.size()]));
+	public static <E extends SQLElement<E>> SQLElementList<E> getByIds(Class<E> elemClass, Integer... ids) throws ORMException {
+		return getByIds(elemClass, Arrays.asList(ids));
 	}
 
-	public static <E extends SQLElement<E>> SQLElementList<E> getByIds(Class<E> elemClass, Integer... ids) throws ORMException {
-		SQLField<E, Integer> idField = getSQLIdField(elemClass);
-		SQLWhereChain where = new SQLWhereOr();
-		for (Integer id : ids)
-			if (id != null) where.or(new SQLWhereComp(idField, SQLComparator.EQ, id));
-		return getAll(elemClass, where, SQLOrderBy.asc(idField), 1, null);
+	public static <E extends SQLElement<E>> SQLElementList<E> getByIds(Class<E> elemClass, Collection<Integer> ids)
+			throws ORMException {
+		return getAll(elemClass, getSQLIdField(elemClass).in(ids), SQLOrderBy.asc(getSQLIdField(elemClass)), 1, null);
 	}
 
 	public static <E extends SQLElement<E>> E getById(Class<E> elemClass, int id) throws ORMException {
-		return getFirst(elemClass, new SQLWhereComp(getSQLIdField(elemClass), SQLComparator.EQ, id));
+		return getFirst(elemClass, getSQLIdField(elemClass).eq(id));
 	}
 
-	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLWhere where)
+	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLWhere<E> where)
 			throws ORMException {
 		return getFirst(elemClass, where, null, null);
 	}
 
-	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLOrderBy orderBy)
+	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLOrderBy<E> orderBy)
 			throws ORMException {
 		return getFirst(elemClass, null, orderBy, null);
 	}
 
-	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLWhere where, SQLOrderBy orderBy)
+	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLWhere<E> where, SQLOrderBy<E> orderBy)
 			throws ORMException {
 		return getFirst(elemClass, where, orderBy, null);
 	}
 
-	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLWhere where, SQLOrderBy orderBy, Integer offset)
+	public static <E extends SQLElement<E>> E getFirst(Class<E> elemClass, SQLWhere<E> where, SQLOrderBy<E> orderBy, Integer offset)
 			throws ORMException {
 		SQLElementList<E> elts = getAll(elemClass, where, orderBy, 1, offset);
 		return (elts.size() == 0) ? null : elts.get(0);
@@ -144,22 +140,22 @@ public final class ORM {
 		return getAll(elemClass, null, null, null, null);
 	}
 
-	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere where) throws ORMException {
+	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere<E> where) throws ORMException {
 		return getAll(elemClass, where, null, null, null);
 	}
 
-	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere where,
-			SQLOrderBy orderBy) throws ORMException {
+	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere<E> where,
+			SQLOrderBy<E> orderBy) throws ORMException {
 		return getAll(elemClass, where, orderBy, null, null);
 	}
 
-	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere where,
-			SQLOrderBy orderBy, Integer limit) throws ORMException {
+	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere<E> where,
+			SQLOrderBy<E> orderBy, Integer limit) throws ORMException {
 		return getAll(elemClass, where, orderBy, limit, null);
 	}
 
-	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere where,
-			SQLOrderBy orderBy, Integer limit, Integer offset) throws ORMException {
+	public static <E extends SQLElement<E>> SQLElementList<E> getAll(Class<E> elemClass, SQLWhere<E> where,
+			SQLOrderBy<E> orderBy, Integer limit, Integer offset) throws ORMException {
 			SQLElementList<E> elmts = new SQLElementList<>();
 			forEach(elemClass, where, orderBy, limit, offset, elmts::add);
 			return elmts;
@@ -169,23 +165,23 @@ public final class ORM {
 		forEach(elemClass, null, null, null, null, action);
 	}
 	
-	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere where,
+	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere<E> where,
 			Consumer<E> action) throws ORMException {
 		forEach(elemClass, where, null, null, null, action);
 	}
 	
-	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere where,
-			SQLOrderBy orderBy, Consumer<E> action) throws ORMException {
+	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere<E> where,
+			SQLOrderBy<E> orderBy, Consumer<E> action) throws ORMException {
 		forEach(elemClass, where, orderBy, null, null, action);
 	}
 	
-	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere where,
-			SQLOrderBy orderBy, Integer limit, Consumer<E> action) throws ORMException {
+	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere<E> where,
+			SQLOrderBy<E> orderBy, Integer limit, Consumer<E> action) throws ORMException {
 		forEach(elemClass, where, orderBy, limit, null, action);
 	}
 	
-	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere where,
-			SQLOrderBy orderBy, Integer limit, Integer offset, Consumer<E> action) throws ORMException {
+	public static <E extends SQLElement<E>> void forEach(Class<E> elemClass, SQLWhere<E> where,
+			SQLOrderBy<E> orderBy, Integer limit, Integer offset, Consumer<E> action) throws ORMException {
 		initTable(elemClass);
 
 		try {
@@ -221,7 +217,7 @@ public final class ORM {
 		return count(elemClass, null);
 	}
 	
-	public static <E extends SQLElement<E>> long count(Class<E> elemClass, SQLWhere where) throws ORMException {
+	public static <E extends SQLElement<E>> long count(Class<E> elemClass, SQLWhere<E> where) throws ORMException {
 		initTable(elemClass);
 
 		try {
@@ -276,11 +272,11 @@ public final class ORM {
 	
 
 	
-	public static <E extends SQLElement<E>> SQLUpdate<E> update(Class<E> elemClass, SQLWhere where) throws ORMException {
+	public static <E extends SQLElement<E>> SQLUpdate<E> update(Class<E> elemClass, SQLWhere<E> where) throws ORMException {
 		return new SQLUpdate<>(elemClass, where);
 	}
 	
-	/* package */ static <E extends SQLElement<E>> int update(Class<E> elemClass, SQLWhere where, Map<SQLField<E, ?>, Object> values) throws ORMException {
+	/* package */ static <E extends SQLElement<E>> int update(Class<E> elemClass, SQLWhere<E> where, Map<SQLField<E, ?>, Object> values) throws ORMException {
 		return new SQLUpdate<>(elemClass, where, values).execute();
 	}
 
@@ -292,7 +288,7 @@ public final class ORM {
 	 * @return The return value of {@link PreparedStatement#executeUpdate()}, for an SQL query {@code DELETE}.
 	 * @throws ORMException
 	 */
-	public static <E extends SQLElement<E>> int delete(Class<E> elemClass, SQLWhere where) throws ORMException {
+	public static <E extends SQLElement<E>> int delete(Class<E> elemClass, SQLWhere<E> where) throws ORMException {
 		initTable(elemClass);
 		
 		if (where == null) {
diff --git a/src/main/java/fr/pandacube/util/orm/SQLElement.java b/src/main/java/fr/pandacube/util/orm/SQLElement.java
index bb54bbb..1fb224b 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLElement.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLElement.java
@@ -21,7 +21,6 @@ import com.google.gson.Gson;
 import com.google.gson.JsonObject;
 
 import fr.pandacube.util.Log;
-import fr.pandacube.util.orm.SQLWhereComp.SQLComparator;
 
 public abstract class SQLElement<E extends SQLElement<E>> {
 	/** cache for fields for each subclass of SQLElement */
@@ -190,8 +189,7 @@ public abstract class SQLElement<E extends SQLElement<E>> {
 	public <T, P extends SQLElement<P>> P getReferencedEntry(SQLFKField<E, T, P> field) throws ORMException {
 		T fkValue = get(field);
 		if (fkValue == null) return null;
-		return ORM.getFirst(field.getForeignElementClass(),
-				new SQLWhereComp(field.getPrimaryField(), SQLComparator.EQ, fkValue), null);
+		return ORM.getFirst(field.getForeignElementClass(), field.getPrimaryField().eq(fkValue), null);
 	}
 
 	/**
@@ -199,11 +197,10 @@ public abstract class SQLElement<E extends SQLElement<E>> {
 	 * @param <F> the table class of the foreign key that reference a primary key of this element.
 	 * @return all elements in the table F for which the specified foreign key value correspond to the primary key of this element.
 	 */
-	public <T, F extends SQLElement<F>> SQLElementList<F> getReferencingForeignEntries(SQLFKField<F, T, E> field, SQLOrderBy orderBy, Integer limit, Integer offset) throws ORMException {
+	public <T, F extends SQLElement<F>> SQLElementList<F> getReferencingForeignEntries(SQLFKField<F, T, E> field, SQLOrderBy<F> orderBy, Integer limit, Integer offset) throws ORMException {
 		T value = get(field.getPrimaryField());
 		if (value == null) return new SQLElementList<>();
-		return ORM.getAll(field.getSQLElementType(),
-				new SQLWhereComp(field, SQLComparator.EQ, value), orderBy, limit, offset);
+		return ORM.getAll(field.getSQLElementType(), field.eq(value), orderBy, limit, offset);
 	}
 
 	public boolean isValidForSave() {
@@ -241,7 +238,7 @@ public abstract class SQLElement<E extends SQLElement<E>> {
 
 				if (modifiedValues.isEmpty()) return;
 				
-				ORM.update((Class<E>)getClass(), new SQLWhereComp(getFieldId(), SQLComparator.EQ, getId()), modifiedValues);
+				ORM.update((Class<E>)getClass(), getFieldId().eq(getId()), modifiedValues);
 			}
 			else { // ajouter dans la base
 
diff --git a/src/main/java/fr/pandacube/util/orm/SQLElementList.java b/src/main/java/fr/pandacube/util/orm/SQLElementList.java
index 27806cd..208aa33 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLElementList.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLElementList.java
@@ -14,7 +14,6 @@ import java.util.stream.Collectors;
 import com.google.gson.JsonArray;
 
 import fr.pandacube.util.Log;
-import fr.pandacube.util.orm.SQLWhereComp.SQLComparator;
 
 /**
  *
@@ -85,8 +84,7 @@ public class SQLElementList<E extends SQLElement<E>> extends ArrayList<E> {
 		Class<E> classEl = (Class<E>)storedEl.get(0).getClass();
 		
 		int ret = ORM.update(classEl,
-				new SQLWhereIn(storedEl.get(0).getFieldId(),
-						storedEl.stream().map(SQLElement::getId).collect(Collectors.toList())
+				storedEl.get(0).getFieldId().in(storedEl.stream().map(SQLElement::getId).collect(Collectors.toList())
 						),
 				modifiedValues);
 
@@ -140,7 +138,7 @@ public class SQLElementList<E extends SQLElement<E>> extends ArrayList<E> {
 	
 	
 	
-	public <T, P extends SQLElement<P>> SQLElementList<P> getReferencedEntries(SQLFKField<E, T, P> foreignKey, SQLOrderBy orderBy) throws ORMException {
+	public <T, P extends SQLElement<P>> SQLElementList<P> getReferencedEntries(SQLFKField<E, T, P> foreignKey, SQLOrderBy<P> orderBy) throws ORMException {
 		Set<T> values = new HashSet<>();
 		forEach(v -> {
 			T val = v.get(foreignKey);
@@ -152,8 +150,8 @@ public class SQLElementList<E extends SQLElement<E>> extends ArrayList<E> {
 			return new SQLElementList<>();
 		}
 		
-		SQLWhereChain where = SQLWhereChain.or();
-		values.forEach(v -> where.or(new SQLWhereComp(foreignKey.getPrimaryField(), SQLComparator.EQ, v)));
+		SQLWhereOr<P> where = SQLWhere.or();
+		values.forEach(v -> where.or(foreignKey.getPrimaryField().eq(v)));
 		
 		
 		return ORM.getAll(foreignKey.getForeignElementClass(), where, orderBy, null, null);
@@ -171,7 +169,7 @@ public class SQLElementList<E extends SQLElement<E>> extends ArrayList<E> {
 	
 
 	
-	public <T, F extends SQLElement<F>> SQLElementList<F> getReferencingForeignEntries(SQLFKField<F, T, E> foreignKey, SQLOrderBy orderBy, Integer limit, Integer offset) throws ORMException {
+	public <T, F extends SQLElement<F>> SQLElementList<F> getReferencingForeignEntries(SQLFKField<F, T, E> foreignKey, SQLOrderBy<F> orderBy, Integer limit, Integer offset) throws ORMException {
 		Set<T> values = new HashSet<>();
 		forEach(v -> {
 			T val = v.get(foreignKey.getPrimaryField());
@@ -183,15 +181,15 @@ public class SQLElementList<E extends SQLElement<E>> extends ArrayList<E> {
 			return new SQLElementList<>();
 		}
 
-		SQLWhereChain where = SQLWhere.or();
-		values.forEach(v -> where.or(new SQLWhereComp(foreignKey, SQLComparator.EQ, v)));
+		SQLWhereOr<F> where = SQLWhere.or();
+		values.forEach(v -> where.or(foreignKey.eq(v)));
 		
 		return ORM.getAll(foreignKey.getSQLElementType(), where, orderBy, limit, offset);
 		
 	}
 
 	
-	public <T, F extends SQLElement<F>> Map<T, SQLElementList<F>> getReferencingForeignEntriesInGroups(SQLFKField<F, T, E> foreignKey, SQLOrderBy orderBy, Integer limit, Integer offset) throws ORMException {
+	public <T, F extends SQLElement<F>> Map<T, SQLElementList<F>> getReferencingForeignEntriesInGroups(SQLFKField<F, T, E> foreignKey, SQLOrderBy<F> orderBy, Integer limit, Integer offset) throws ORMException {
 		SQLElementList<F> foreignElements = getReferencingForeignEntries(foreignKey, orderBy, limit, offset);
 		
 		Map<T, SQLElementList<F>> map = new HashMap<>();
diff --git a/src/main/java/fr/pandacube/util/orm/SQLField.java b/src/main/java/fr/pandacube/util/orm/SQLField.java
index 4e73199..2a53907 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLField.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLField.java
@@ -92,43 +92,43 @@ public class SQLField<E extends SQLElement<E>, T> {
 
 	
 	
-	public SQLWhere eq(T r) {
+	public SQLWhere<E> eq(T r) {
 		return comp(SQLComparator.EQ, r);
 	}
-	public SQLWhere geq(T r) {
+	public SQLWhere<E> geq(T r) {
 		return comp(SQLComparator.GEQ, r);
 	}
-	public SQLWhere gt(T r) {
+	public SQLWhere<E> gt(T r) {
 		return comp(SQLComparator.GT, r);
 	}
-	public SQLWhere leq(T r) {
+	public SQLWhere<E> leq(T r) {
 		return comp(SQLComparator.LEQ, r);
 	}
-	public SQLWhere lt(T r) {
+	public SQLWhere<E> lt(T r) {
 		return comp(SQLComparator.LT, r);
 	}
-	public SQLWhere neq(T r) {
+	public SQLWhere<E> neq(T r) {
 		return comp(SQLComparator.NEQ, r);
 	}
 	
-	private SQLWhere comp(SQLComparator c, T r) {
-		return new SQLWhereComp(this, c, r);
+	private SQLWhere<E> comp(SQLComparator c, T r) {
+		return new SQLWhereComp<>(this, c, r);
 	}
 	
 	
 	
-	public SQLWhere in(Collection<T> v) {
-		return new SQLWhereIn(this, v);
+	public SQLWhere<E> in(Collection<T> v) {
+		return new SQLWhereIn<>(this, v);
 	}
 	
 	
 
-	public SQLWhere isNull() {
-		return new SQLWhereNull(this, true);
+	public SQLWhere<E> isNull() {
+		return new SQLWhereNull<>(this, true);
 	}
 	
-	public SQLWhere isNotNull() {
-		return new SQLWhereNull(this, false);
+	public SQLWhere<E> isNotNull() {
+		return new SQLWhereNull<>(this, false);
 	}
 
 }
diff --git a/src/main/java/fr/pandacube/util/orm/SQLOrderBy.java b/src/main/java/fr/pandacube/util/orm/SQLOrderBy.java
index 401337a..2e98c48 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLOrderBy.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLOrderBy.java
@@ -3,7 +3,7 @@ package fr.pandacube.util.orm;
 import java.util.ArrayList;
 import java.util.List;
 
-public class SQLOrderBy {
+public class SQLOrderBy<E extends SQLElement<E>> {
 
 	private List<OBField> orderByFields = new ArrayList<>();
 
@@ -19,7 +19,7 @@ public class SQLOrderBy {
 	 * @param d le sens de tri (croissant ASC ou décroissant DESC)
 	 * @return l'objet courant (permet de chainer les ajouts de champs)
 	 */
-	private SQLOrderBy add(SQLField<?, ?> field, Direction d) {
+	private SQLOrderBy<E> add(SQLField<E, ?> field, Direction d) {
 		orderByFields.add(new OBField(field, d));
 		return this;
 	}
@@ -30,7 +30,7 @@ public class SQLOrderBy {
 	 * @param field le champ SQL à ordonner
 	 * @return l'objet courant (permet de chainer les ajouts de champs)
 	 */
-	public SQLOrderBy thenAsc(SQLField<?, ?> field) {
+	public SQLOrderBy<E> thenAsc(SQLField<E, ?> field) {
 		return add(field, Direction.ASC);
 	}
 
@@ -40,7 +40,7 @@ public class SQLOrderBy {
 	 * @param field le champ SQL à ordonner
 	 * @return l'objet courant (permet de chainer les ajouts de champs)
 	 */
-	public SQLOrderBy thenDesc(SQLField<?, ?> field) {
+	public SQLOrderBy<E> thenDesc(SQLField<E, ?> field) {
 		return add(field, Direction.DESC);
 	}
 
@@ -61,10 +61,10 @@ public class SQLOrderBy {
 	}
 
 	private class OBField {
-		public final SQLField<?, ?> field;
+		public final SQLField<E, ?> field;
 		public final Direction direction;
 
-		public OBField(SQLField<?, ?> f, Direction d) {
+		public OBField(SQLField<E, ?> f, Direction d) {
 			field = f;
 			direction = d;
 		}
@@ -83,12 +83,12 @@ public class SQLOrderBy {
 	
 
 	
-	public static SQLOrderBy asc(SQLField<?, ?> field) {
-		return new SQLOrderBy().thenAsc(field);
+	public static <E extends SQLElement<E>> SQLOrderBy<E> asc(SQLField<E, ?> field) {
+		return new SQLOrderBy<E>().thenAsc(field);
 	}
 	
-	public static SQLOrderBy desc(SQLField<?, ?> field) {
-		return new SQLOrderBy().thenDesc(field);
+	public static <E extends SQLElement<E>> SQLOrderBy<E> desc(SQLField<E, ?> field) {
+		return new SQLOrderBy<E>().thenDesc(field);
 	}
 	
 	
diff --git a/src/main/java/fr/pandacube/util/orm/SQLUpdate.java b/src/main/java/fr/pandacube/util/orm/SQLUpdate.java
index 295ab2f..b1922ec 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLUpdate.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLUpdate.java
@@ -12,16 +12,16 @@ import fr.pandacube.util.Log;
 public class SQLUpdate<E extends SQLElement<E>> {
 	
 	private final Class<E> elemClass;
-	private final SQLWhere where;
+	private final SQLWhere<E> where;
 	private final Map<SQLField<E, ?>, Object> values;
 	
-	/* package */ SQLUpdate(Class<E> el, SQLWhere w) {
+	/* package */ SQLUpdate(Class<E> el, SQLWhere<E> w) {
 		elemClass = el;
 		where = w;
 		values = new HashMap<>();
 	}
 	
-	/* package */ SQLUpdate(Class<E> el, SQLWhere w, Map<SQLField<E, ?>, Object> v) {
+	/* package */ SQLUpdate(Class<E> el, SQLWhere<E> w, Map<SQLField<E, ?>, Object> v) {
 		elemClass = el;
 		where = w;
 		values = v;
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhere.java b/src/main/java/fr/pandacube/util/orm/SQLWhere.java
index 6819cde..74641b3 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhere.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhere.java
@@ -6,7 +6,7 @@ import org.javatuples.Pair;
 
 import fr.pandacube.util.Log;
 
-public abstract class SQLWhere {
+public abstract class SQLWhere<E extends SQLElement<E>> {
 
 	public abstract Pair<String, List<Object>> toSQL() throws ORMException;
 
@@ -20,26 +20,26 @@ public abstract class SQLWhere {
 		}
 	}
 	
-	public SQLWhereAnd and(SQLWhere other) {
-		return and().and(this).and(other);
+	public SQLWhereAnd<E> and(SQLWhere<E> other) {
+		return new SQLWhereAnd<E>().and(this).and(other);
 	}
 	
-	public SQLWhereOr or(SQLWhere other) {
-		return or().or(this).or(other);
+	public SQLWhereOr<E> or(SQLWhere<E> other) {
+		return new SQLWhereOr<E>().or(this).or(other);
 	}
 	
-	public static SQLWhereAnd and() {
-		return new SQLWhereAnd();
+	public static <E extends SQLElement<E>> SQLWhereAnd<E> and() {
+		return new SQLWhereAnd<>();
 	}
 	
-	public static SQLWhereOr or() {
-		return new SQLWhereOr();
+	public static <E extends SQLElement<E>> SQLWhereOr<E> or() {
+		return new SQLWhereOr<>();
 	}
 	
 	
 	
-	public static SQLWhere like(SQLField<?, String> f, String like) {
-		return new SQLWhereLike(f, like);
+	public static <E extends SQLElement<E>> SQLWhere<E> like(SQLField<E, String> f, String like) {
+		return new SQLWhereLike<E>(f, like);
 	}
 
 }
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereAnd.java b/src/main/java/fr/pandacube/util/orm/SQLWhereAnd.java
index b71cdf2..b30966a 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereAnd.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereAnd.java
@@ -1,14 +1,15 @@
 package fr.pandacube.util.orm;
 
-public class SQLWhereAnd extends SQLWhereChain {
+public class SQLWhereAnd<E extends SQLElement<E>> extends SQLWhereChain<E> {
 
 	/* package */ SQLWhereAnd() {
 		super(SQLBoolOp.AND);
 	}
 	
 	@Override
-	public SQLWhereAnd and(SQLWhere other) {
-		return (SQLWhereAnd) add(other);
+	public SQLWhereAnd<E> and(SQLWhere<E> other) {
+		add(other);
+		return this;
 	}
 
 }
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereChain.java b/src/main/java/fr/pandacube/util/orm/SQLWhereChain.java
index b482405..550f72a 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereChain.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereChain.java
@@ -5,20 +5,19 @@ import java.util.List;
 
 import org.javatuples.Pair;
 
-public abstract class SQLWhereChain extends SQLWhere {
+public abstract class SQLWhereChain<E extends SQLElement<E>> extends SQLWhere<E> {
 
 	private SQLBoolOp operator;
-	protected List<SQLWhere> conditions = new ArrayList<>();
+	protected List<SQLWhere<E>> conditions = new ArrayList<>();
 
 	/* package */ SQLWhereChain(SQLBoolOp op) {
 		if (op == null) throw new IllegalArgumentException("op can't be null");
 		operator = op;
 	}
 
-	protected SQLWhereChain add(SQLWhere sqlWhere) {
+	protected void add(SQLWhere<E> sqlWhere) {
 		if (sqlWhere == null) throw new IllegalArgumentException("sqlWhere can't be null");
 		conditions.add(sqlWhere);
-		return this;
 	}
 	
 	@Override
@@ -31,7 +30,7 @@ public abstract class SQLWhereChain extends SQLWhere {
 		List<Object> params = new ArrayList<>();
 		boolean first = true;
 
-		for (SQLWhere w : conditions) {
+		for (SQLWhere<E> w : conditions) {
 			if (!first) sql += " " + operator.sql + " ";
 			first = false;
 
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereComp.java b/src/main/java/fr/pandacube/util/orm/SQLWhereComp.java
index 2c719a7..bbe481e 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereComp.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereComp.java
@@ -5,7 +5,7 @@ import java.util.List;
 
 import org.javatuples.Pair;
 
-/* package */ class SQLWhereComp extends SQLWhere {
+/* package */ class SQLWhereComp<E extends SQLElement<E>> extends SQLWhere<E> {
 
 	private SQLField<?, ?> left;
 	private SQLComparator comp;
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereIn.java b/src/main/java/fr/pandacube/util/orm/SQLWhereIn.java
index 526746f..bb1197b 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereIn.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereIn.java
@@ -6,12 +6,12 @@ import java.util.List;
 
 import org.javatuples.Pair;
 
-/* package */ class SQLWhereIn extends SQLWhere {
+/* package */ class SQLWhereIn<E extends SQLElement<E>> extends SQLWhere<E> {
 
-	private SQLField<?, ?> field;
+	private SQLField<E, ?> field;
 	private Collection<?> values;
 
-	/* package */ <T> SQLWhereIn(SQLField<?, T> f, Collection<T> v) {
+	/* package */ <T> SQLWhereIn(SQLField<E, T> f, Collection<T> v) {
 		if (f == null || v == null)
 			throw new IllegalArgumentException("All arguments for SQLWhereIn constructor can't be null");
 		field = f;
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereLike.java b/src/main/java/fr/pandacube/util/orm/SQLWhereLike.java
index 4aa2e0c..85dde1f 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereLike.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereLike.java
@@ -5,9 +5,9 @@ import java.util.List;
 
 import org.javatuples.Pair;
 
-/* package */ class SQLWhereLike extends SQLWhere {
+/* package */ class SQLWhereLike<E extends SQLElement<E>> extends SQLWhere<E> {
 
-	private SQLField<?, String> field;
+	private SQLField<E, String> field;
 	private String likeExpr;
 
 	/**
@@ -16,7 +16,7 @@ import org.javatuples.Pair;
 	 * @param f the field at left of the LIKE keyword. Can't be null
 	 * @param like the like expression.
 	 */
-	/* package */ SQLWhereLike(SQLField<?, String> f, String like) {
+	/* package */ SQLWhereLike(SQLField<E, String> f, String like) {
 		if (f == null || like == null)
 			throw new IllegalArgumentException("All arguments for SQLWhereLike constructor can't be null");
 		field = f;
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereNull.java b/src/main/java/fr/pandacube/util/orm/SQLWhereNull.java
index b8cb409..a78b6c8 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereNull.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereNull.java
@@ -8,9 +8,9 @@ import org.javatuples.Pair;
 
 import fr.pandacube.util.Log;
 
-/* package */ class SQLWhereNull extends SQLWhere {
+/* package */ class SQLWhereNull<E extends SQLElement<E>> extends SQLWhere<E> {
 
-	private SQLField<?, ?> fild;
+	private SQLField<E, ?> fild;
 	private boolean nulll;
 
 	/**
@@ -20,7 +20,7 @@ import fr.pandacube.util.Log;
 	 * @param isNull true if we want to ckeck if "IS NULL", or false to check if
 	 *        "IS NOT NULL"
 	 */
-	/* package */ SQLWhereNull(SQLField<?, ?> field, boolean isNull) {
+	/* package */ SQLWhereNull(SQLField<E, ?> field, boolean isNull) {
 		if (field == null) throw new IllegalArgumentException("field can't be null");
 		if (!field.canBeNull) Log.getLogger().log(Level.WARNING,
 				"Useless : Trying to check IS [NOT] NULL on the field " + field.getSQLElementType().getName() + "#"
diff --git a/src/main/java/fr/pandacube/util/orm/SQLWhereOr.java b/src/main/java/fr/pandacube/util/orm/SQLWhereOr.java
index d64a409..6cb4ab4 100644
--- a/src/main/java/fr/pandacube/util/orm/SQLWhereOr.java
+++ b/src/main/java/fr/pandacube/util/orm/SQLWhereOr.java
@@ -1,14 +1,15 @@
 package fr.pandacube.util.orm;
 
-public class SQLWhereOr extends SQLWhereChain {
+public class SQLWhereOr<E extends SQLElement<E>> extends SQLWhereChain<E> {
 
 	/* package */ SQLWhereOr() {
 		super(SQLBoolOp.OR);
 	}
 	
 	@Override
-	public SQLWhereOr or(SQLWhere other) {
-		return (SQLWhereOr) add(other);
+	public SQLWhereOr<E> or(SQLWhere<E> other) {
+		add(other);
+		return this;
 	}
 
 }