improved oracle sql parser support fetch clause. issue #1448

src/main/java/com/alibaba/druid/sql/ast/statement/SQLSelectQueryBlock.java

@@ -37,6 +37,7 @@ public class SQLSelectQueryBlock extends SQLObjectImpl implements SQLSelectQuery
     protected boolean                   forUpdate     = false;
     protected boolean                   noWait        = false;
     protected SQLExpr                   waitTime;
+    protected SQLExpr                   first;
 
     public SQLSelectQueryBlock(){
 
@@ -142,9 +143,24 @@ public class SQLSelectQueryBlock extends SQLObjectImpl implements SQLSelectQuery
     }
     
     public void setWaitTime(SQLExpr waitTime) {
+        if (waitTime != null) {
+            waitTime.setParent(this);
+        }
         this.waitTime = waitTime;
     }
 
+
+    public SQLExpr getFirst() {
+        return first;
+    }
+
+    public void setFirst(SQLExpr first) {
+        if (first != null) {
+            first.setParent(this);
+        }
+        this.first = first;
+    }
+
 	@Override
     protected void accept0(SQLASTVisitor visitor) {
         if (visitor.visit(this)) {