From 775d29f3ddb3744019e40d548bb6fd05b00f268c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=AB=98=E9=93=81?= <szujobs@gmail.com>
Date: Tue, 3 Oct 2017 14:46:30 -0500
Subject: [PATCH] Updated Druid_SQL_AST (markdown)

---
 Druid_SQL_AST.md | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/Druid_SQL_AST.md b/Druid_SQL_AST.md
index ae51e24..bc02edf 100644
--- a/Druid_SQL_AST.md
+++ b/Druid_SQL_AST.md
@@ -114,6 +114,26 @@ class SQLWithSubqueryClause {
 }
 ```
 
+## 2.4
+```java
+interface SQLSelectQuery extends SQLObject {}
+
+class SQLSelectQueryBlock implements SQLSelectQuery {
+    List<SQLSelectItem> selectList;
+    SQLTableSource from;
+    SQLExprTableSource into;
+    SQLExpr where;
+    SQLSelectGroupByClause groupBy;
+    SQLOrderBy orderBy;
+    SQLLimit limit;
+}
+
+class SQLUnionQuery implements SQLSelectQuery {
+    SQLSelectQuery left;
+    SQLSelectQuery right;
+    SQLUnionOperator operator; // UNION/UNION_ALL/MINUS/INTERSECT
+}
+```
 
 # 3. 怎样产生AST