refactor

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

@@ -211,8 +211,6 @@ public class SQLExprParser extends SQLParser {
                 sqlExpr = new SQLDefaultExpr();
                 lexer.nextToken();
                 break;
-            case USER:
-            case PASSWORD:
             case DUAL:
             case KEY:
             case DISTINCT:

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

@@ -121,7 +121,7 @@ public class SQLStatementParser extends SQLParser {
 
                     statementList.add(stmt);
                     continue;
-                } else if (lexer.token() == Token.USER) {
+                } else if (identifierEquals("USER")) {
                     SQLStatement stmt = parseDropUser();
                     statementList.add(stmt);
                     continue;

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

@@ -67,7 +67,6 @@ public enum Token {
     ON("ON"), 
     SCHEMA("SCHEMA"), 
     CAST("CAST"),
-    USER("USER"),
     COLUMN("COLUMN"),
     USE("USE"),