imporved odps sql parser. fixed issue #1307

src/main/java/com/alibaba/druid/sql/dialect/odps/parser/OdpsLexer.java

@@ -320,4 +320,8 @@ public class OdpsLexer extends Lexer {
         
         super.scanVariable();
     }
+    
+    protected final void scanString() {
+        scanString2();
+    }
 }

src/main/java/com/alibaba/druid/sql/dialect/odps/visitor/OdpsOutputVisitor.java

@@ -25,6 +25,7 @@ import com.alibaba.druid.sql.ast.SQLOrderBy;
 import com.alibaba.druid.sql.ast.SQLSetQuantifier;
 import com.alibaba.druid.sql.ast.SQLStatement;
 import com.alibaba.druid.sql.ast.expr.SQLCaseExpr;
+import com.alibaba.druid.sql.ast.expr.SQLCharExpr;
 import com.alibaba.druid.sql.ast.expr.SQLMethodInvokeExpr;
 import com.alibaba.druid.sql.ast.statement.SQLAssignItem;
 import com.alibaba.druid.sql.ast.statement.SQLColumnDefinition;
@@ -874,4 +875,18 @@ public class OdpsOutputVisitor extends SQLASTOutputVisitor implements OdpsASTVis
         decrementIndent();
         return false;
     }
+    
+    public boolean visit(SQLCharExpr x) {
+        String text = x.getText();
+        if (text == null) {
+            print0(ucase ? "NULL" : "null");
+        } else {
+            print('\'');
+            String text2 = text.replaceAll("\\'", "\\\\'");
+            print0(text2);
+            print('\'');
+        }
+
+        return false;
+    }
 }