improved PageUtils.hasUnorderedLimit.

src/main/java/com/alibaba/druid/sql/PagerUtils.java

@@ -527,7 +527,22 @@ public class PagerUtils {
             SQLLimit limit = x.getLimit();
 
             if (limit != null && (orderBy == null || orderBy.getItems().size() == 0)) {
-                unorderedLimitCount++;
+                boolean subQueryHasOrderBy = false;
+                SQLTableSource from = x.getFrom();
+                if (from instanceof SQLSubqueryTableSource) {
+                    SQLSubqueryTableSource subqueryTabSrc = (SQLSubqueryTableSource) from;
+                    SQLSelect select = subqueryTabSrc.getSelect();
+                    if (select.getQuery() instanceof SQLSelectQueryBlock) {
+                        SQLSelectQueryBlock subquery = (SQLSelectQueryBlock) select.getQuery();
+                        if (subquery.getOrderBy() != null && subquery.getOrderBy().getItems().size() > 0) {
+                            subQueryHasOrderBy = true;
+                        }
+                    }
+                }
+
+                if (!subQueryHasOrderBy) {
+                    unorderedLimitCount++;
+                }
             }
             return true;
         }

src/test/java/com/alibaba/druid/bvt/sql/PagerUtilsTest_hasUnorderedLimit.java

@@ -26,4 +26,9 @@ public class PagerUtilsTest_hasUnorderedLimit extends TestCase {
         String sql = "select * from(select * from test t limit 3) x";
         assertTrue(PagerUtils.hasUnorderedLimit(sql, JdbcConstants.MYSQL));
     }
+
+    public void test_true_subquery_2() throws Exception {
+        String sql = "select * from (select * from test t order by id desc) z limit 100";
+        assertFalse(PagerUtils.hasUnorderedLimit(sql, JdbcConstants.MYSQL));
+    }
 }