Fix alter table index descending (#2387)

Author: dengliming

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -9621,11 +9621,13 @@ String AList():
 String ColumnsNamesListItem():
 {
 	Token tk = null;
+    Token sortDirection = null;
     String item = null;
 }
 {
 	( item = RelObjectName() )
 	[ LOOKAHEAD(2)  "(" tk = <S_LONG>  ")" { item = item + "(" + tk.image + ")"; } ]
+    [ (sortDirection = <K_ASC> | sortDirection = <K_DESC>) { item = item + " " + sortDirection.image; } ]
 	{
 		return item;
 	}

src/test/java/net/sf/jsqlparser/statement/alter/AlterTest.java

@@ -572,6 +572,17 @@ public void testAlterTableIndex586() throws Exception {
                 + "USING BTREE, ALGORITHM = INPLACE", result.toString());
     }
 
+    @Test
+    public void testAlterTableDropAndAddUniqueIndexWithAscendingColumns() throws Exception {
+        Statement result =
+                CCJSqlParserUtil.parse("ALTER TABLE `wxp_dm`.`xqgl_req_report` "
+                        + "DROP INDEX `index_name`, "
+                        + "ADD UNIQUE INDEX `index_name`(`report_name` ASC) USING BTREE");
+        assertEquals("ALTER TABLE `wxp_dm`.`xqgl_req_report` DROP INDEX `index_name`, "
+                + "ADD UNIQUE INDEX `index_name` (`report_name` ASC) USING BTREE",
+                result.toString());
+    }
+
     @Test
     public void testIssue259() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed(