Question

我在任何地方都找不到类似的问题，也没有类似的答案，经过数小时的搜索，我终于找到了解决方法。

问题：

在Java本机查询中使用UNION并具有列的值，该值始终为空字符串（''）

（一个简单的虚拟示例）查询字符串

String queryString = "SELECT * FROM ( " +
    "    SELECT  " +
    "        a_type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        lent_value as 'Credits', " +
    "        '' as 'Payment Info' " +
    "    FROM free_users " +
    "    UNION " +
    "    SELECT  " +
    "        type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        value as 'Credits', " +
    "        payment_info as 'Payment Info' " +
    "    FROM paid_users " +
    ") results " +
    "ORDER BY results.`Full Name` ";

使用实体管理器创建查询

Query query = entityManager.createNativeQuery(queryString);

并执行它

query.getResultList();

在StringIndexOutOfBoundsException中返回的错误消息为错误消息String index out of range: 0

发生此问题是由于 first SELECT中具有空字符串列。

休眠状态与 first SELECT的''值不匹配，因此以下UNION失败。

该列的值必须至少为 ，且字符串长度为1个字符

更正的查询字符串

String correctedQueryString = "SELECT * FROM ( " +
    "    SELECT  " +
    "        a_type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        lent_value as 'Credits', " +
    "        'p' as 'Payment Info' " +
    "    FROM free_users " +
    "    UNION " +
    "    SELECT  " +
    "        type as 'Contract Type', " +
    "        name as 'Full Name', " +
    "        value as 'Credits', " +
    "        payment_info as 'Payment Info' " +
    "    FROM paid_users " +
    ") results " +
    "ORDER BY results.`Full Name` ";

Java Spring StringIndexOutOfBoundsException，而在NativeQuery中使用UNION

0 个答案: