improve sqlwall rule

src/main/java/com/alibaba/druid/sql/parser/Keywords.java

@@ -35,9 +35,9 @@ public class Keywords {
         map.put("AND", Token.AND);
         map.put("ANY", Token.ANY);
         map.put("AS", Token.AS);
-        
+
         map.put("ENABLE", Token.ENABLE);
-        map.put("DISABLE", Token. DISABLE);
+        map.put("DISABLE", Token.DISABLE);
 
         map.put("ASC", Token.ASC);
         map.put("BETWEEN", Token.BETWEEN);
@@ -61,6 +61,7 @@ public class Keywords {
         map.put("DROP", Token.DROP);
         map.put("ELSE", Token.ELSE);
         map.put("EXPLAIN", Token.EXPLAIN);
+        map.put("EXCEPT", Token.EXCEPT);
 
         map.put("END", Token.END);
         map.put("ESCAPE", Token.ESCAPE);
@@ -121,18 +122,18 @@ public class Keywords {
         map.put("WHEN", Token.WHEN);
         map.put("WHERE", Token.WHERE);
         map.put("XOR", Token.XOR);
-        
+
         map.put("OVER", Token.OVER);
         map.put("TO", Token.TO);
         map.put("USE", Token.USE);
-        
+
         map.put("REPLACE", Token.REPLACE);
-        
+
         map.put("COMMENT", Token.COMMENT);
         map.put("COMPUTE", Token.COMPUTE);
         map.put("WITH", Token.WITH);
         map.put("GRANT", Token.GRANT);
-        
+
         DEFAULT_KEYWORDS = new Keywords(map);
     }
 

src/main/java/com/alibaba/druid/sql/parser/SQLSelectParser.java

@@ -62,7 +62,7 @@ public class SQLSelectParser extends SQLParser {
         if (select.getOrderBy() == null) {
             select.setOrderBy(parseOrderBy());
         }
-        
+
         if (lexer.token() == Token.HINT) {
             this.exprParser.parseHints(select.getHints());
         }
@@ -103,6 +103,20 @@ public class SQLSelectParser extends SQLParser {
             return unionRest(union);
         }
 
+        if (lexer.token() == Token.EXCEPT) {
+            lexer.nextToken();
+
+            SQLUnionQuery union = new SQLUnionQuery();
+            union.setLeft(selectQuery);
+
+            union.setOperator(SQLUnionOperator.EXCEPT);
+
+            SQLSelectQuery right = this.query();
+            union.setRight(right);
+
+            return union;
+        }
+
         if (lexer.token() == Token.INTERSECT) {
             lexer.nextToken();
 
@@ -145,7 +159,7 @@ public class SQLSelectParser extends SQLParser {
         }
 
         accept(Token.SELECT);
-        
+
         if (lexer.token() == Token.COMMENT) {
             lexer.nextToken();
         }

src/main/java/com/alibaba/druid/sql/parser/Token.java

@@ -73,6 +73,7 @@ public enum Token {
    
     ALL("ALL"), 
     UNION("UNION"), 
+    EXCEPT("EXCEPT"), 
     INTERSECT("INTERSECT"), 
     MINUS("MINUS"),
     INNER("INNER"),