エラーコード:1582 Incorrect parameter count in the call to native function'str_to_date'

1.エラー記述

1 queries executed, 0 success, 1 errors, 0 warnings

  ：SELECT t.`name`, DATE_FORMAT(str_to_date('2015'), '%Y') as statisDate, ROUND(IFNULL(SUM(t.`amount`), 0), 3) AS ...

    ： 1582
Incorrect parameter count in the call to native function 'str_to_date'

       : 0 sec
       : 0 sec
         : 0 sec

2.エラーの原因

SELECT 
  t.`name`,
  DATE_FORMAT(STR_TO_DATE('2015'), '%Y') AS statisDate,
  ROUND(IFNULL(SUM(t.`amount`), 0), 3) AS amount
FROM
  t_stu_info t 
WHERE 1 = 1 
  AND DATE_FORMAT(t.statisDate, '%Y') = '2015' 
UNION
ALL 
SELECT 
  t.`name`,
  DATE_FORMAT(STR_TO_DATE('2014'), '%Y') AS statisDate,
  ROUND(IFNULL(SUM(t.`amount`), 0), 3) AS amount
FROM
  t_stu_info t 
WHERE 1 = 1 
  AND DATE_FORMAT(t.statisDate, '%Y') = '2014'

MySQL内蔵関数str_to_dateのフォーマットはstr_to_date(文字列、日付フォーマット);このクエリSQLではstr_to_date(文字列)、エラー
3.解決策
クエリSQL文の変更

SELECT 
  t.`name`,
  DATE_FORMAT(STR_TO_DATE('2015','%Y'), '%Y') AS statisDate,
  ROUND(IFNULL(SUM(t.`amount`), 0), 3) AS amount
FROM
  t_stu_info t 
WHERE 1 = 1 
  AND DATE_FORMAT(t.statisDate, '%Y') = '2015' 
UNION
ALL 
SELECT 
  t.`name`,
  DATE_FORMAT(STR_TO_DATE('2014','%Y'), '%Y') AS statisDate,
  ROUND(IFNULL(SUM(t.`amount`), 0), 3) AS amount
FROM
  t_stu_info t 
WHERE 1 = 1 
  AND DATE_FORMAT(t.statisDate, '%Y') = '2014'