这段代码if (account_str == CT2A(account) && password_str == CT2A(password))报错显示没有与这些操作数匹配的“==”运算符,如何修改这段代码使它能够运行
时间: 2023-10-03 13:09:17 浏览: 54
这个错误通常是由于比较的两个操作数类型不匹配所导致的。在这段代码中,`account_str`和`password_str`的类型可能是`CString`或者`std::string`,而`CT2A(account)`和`CT2A(password)`返回的类型可能是`const char*`或者`char*`,这两种类型与`CString`或者`std::string`不匹配,因此编译器会报错。
要解决这个问题,可以使用`CString`或者`std::string`的成员函数`GetString()`或者`c_str()`将它们转换为`const char*`类型的指针,然后再进行比较。修改后的代码如下所示:
```
if (account_str.GetString() == CT2A(account) && password_str.GetString() == CT2A(password))
```
或者:
```
if (account_str.c_str() == CT2A(account) && password_str.c_str() == CT2A(password))
```
这样就可以避免类型不匹配的问题,使代码能够正常运行。
相关问题
优化这段SQL:SELECT CONCAT( HOUR ( mail_send_time ) DIV 1 * 1, ':00-', HOUR ( mail_send_time ) DIV 1 * 1, ':59' ) AS timeInterval, IFNULL( COUNT( * ), 0 ) AS total, IFNULL( SUM( contact_account_type = IF(cv.code_value='01',cv.code_description,'') ), 0 ) AS wxTotal, IFNULL( SUM( contact_account_type = IF(cv.code_value='02',cv.code_description,'') ), 0 ) AS qqTotal, IFNULL( SUM( local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,'')), 0 ) AS wxSend, IFNULL( SUM( local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,'')), 0 ) AS wxReceive , IFNULL( SUM( local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,'')), 0 ) AS qqSend, IFNULL( SUM( local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,'')), 0 ) AS qqReceive FROM dwd_t_friend_talk, dwd_t_code_value cv WHERE person_no = '653129200105072624' AND contact_account_type IN ( IF(cv.code_value='01',cv.code_description,''), IF(cv.code_value='02',cv.code_description,'')) AND friend_account <> '' AND contact_account_type <> '' AND mail_send_time IS NOT NULL AND mail_send_time <> '' GROUP BY HOUR ( mail_send_time ) DIV 1
可以考虑以下几种优化方式:
1. 使用JOIN语句代替WHERE语句中的子查询,可以提高查询效率。
2. 对mail_send_time字段创建索引,可以加快查询速度。
3. 可以尝试将COUNT和SUM聚合函数合并成一个SELECT语句,以减少查询次数。
4. 可以考虑将IFNULL函数替换为COALESCE函数,因为COALESCE函数在MySQL中的性能更好。
优化后的SQL如下:
SELECT CONCAT(HOUR(mail_send_time) DIV 1 * 1, ':00-', HOUR(mail_send_time) DIV 1 * 1, ':59') AS timeInterval,
COUNT(*) AS total,
SUM(COALESCE(contact_account_type = IF(cv.code_value='01',cv.code_description,''), 0)) AS wxTotal,
SUM(COALESCE(contact_account_type = IF(cv.code_value='02',cv.code_description,''), 0)) AS qqTotal,
SUM(COALESCE(local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,''), 0)) AS wxSend,
SUM(COALESCE(local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='01',cv.code_description,''), 0)) AS wxReceive,
SUM(COALESCE(local_action = IF(cv.code_value='05',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,''), 0)) AS qqSend,
SUM(COALESCE(local_action = IF(cv.code_value='06',cv.code_description,'') AND contact_account_type = IF(cv.code_value='02',cv.code_description,''), 0)) AS qqReceive
FROM dwd_t_friend_talk
JOIN dwd_t_code_value cv ON contact_account_type IN (cv.code_description)
WHERE person_no = '653129200105072624'
AND friend_account <> ''
AND contact_account_type <> ''
AND mail_send_time IS NOT NULL
AND mail_send_time <> ''
GROUP BY HOUR(mail_send_time) DIV 1;
SELECT count (*) FROM T_SERVICE_ORDER WHERE ACCOUNT_NO=:1 or SUPER_ACCOUNT_NO =:2这个语法正确吗如何getInt到count值
这语法是正确的。它查询了 `T_SERVICE_ORDER` 表中 `ACCOUNT_NO` 等于 `:1` 或者 `SUPER_ACCOUNT_NO` 等于 `:2` 的行数。如果要获取查询结果中的 `count` 值,可以使用 JDBC 中的 `getInt` 方法。示例代码如下:
```java
try {
// 假设已经创建好了 Connection 对象 conn,并且传入了参数 :1 和 :2
String sql = "SELECT count(*) FROM T_SERVICE_ORDER WHERE ACCOUNT_NO=:1 or SUPER_ACCOUNT_NO=:2";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1, "account_no_value");
pstmt.setString(2, "super_account_no_value");
ResultSet rs = pstmt.executeQuery();
if(rs.next()) {
int count = rs.getInt(1);
System.out.println("查询结果 count 值为:" + count);
}
} catch (SQLException e) {
e.printStackTrace();
}
```
其中,`rs.getInt(1)` 表示获取查询结果集中第一列的值,即 `count` 值。
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