improve alter table statment

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlExprParser.java

@@ -1849,7 +1849,10 @@ public class MySqlExprParser extends SQLExprParser {
                         lexer.nextToken();
                     }
 
-                    assignItem = new SQLAssignItem(new SQLIdentifierExpr(SINGLE_WORD_TABLE_OPTIONS[idx]), expr());
+                    // STORAGE_POLICY
+                    assignItem = new SQLAssignItem(
+                            new SQLIdentifierExpr(SINGLE_WORD_TABLE_OPTIONS[idx])
+                            , idx == 9 ? charExpr() : expr());
                 }
             } else {
                 // Following may not table options. Save mark.

src/test/java/com/alibaba/druid/bvt/sql/mysql/alterTable/MySqlAlterTableTest54.java

@@ -68,4 +68,24 @@ public class MySqlAlterTableTest54 extends TestCase {
             //do nothing
         }
     }
+
+    public void test_6() throws Exception {
+        String sql = "alter table event_log storage_policy = HOT";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        try {
+            SQLAlterTableStatement stmt = (SQLAlterTableStatement) parser.parseStatementList().get(0);
+            fail();
+        } catch (Exception e) {
+        }
+    }
+
+    public void test_7() throws Exception {
+        String sql = "alter table event_log storage_policy = COLD";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        try {
+            SQLAlterTableStatement stmt = (SQLAlterTableStatement) parser.parseStatementList().get(0);
+            fail();
+        } catch (Exception e) {
+        }
+    }
 }