更新行时出现 SQL 错误

Question

正在考虑的表格的详细信息：

用于更新行的代码是：

 public void updateEmployeeDetails(Employee employee) {

    Connection conn = JDBCUtility.getConnection();

    try {
        String updateSql = "UPDATE EMPLOYEE_INFO SET emp_name=?, location=?, email=?, dob=? WHERE emp_id=?";

        PreparedStatement ps = (PreparedStatement)conn.prepareStatement(updateSql);
        ps.setString(1, employee.getEmp_name()); /*all the attributes of employee object are of type String */
        ps.setString(2, employee.getLocation());
        ps.setString(3, employee.getEmail());
        ps.setString(4, employee.getDob());
        ps.setString(5, employee.getEmp_id());
        ps.executeUpdate(updateSql);

    } catch (SQLException e) {
        System.out.println(e.getErrorCode());
        e.printStackTrace();
    }
}

收到错误：

com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?, location=?, email=?, dob=? WHERE  emp_id=?' at line 1

谁能指出错误，因为我仔细检查了查询字符串中的任何可能错误？ mysql的varchar(45)和Java的String兼容吗？即ps.setString(column_index, String) 会是错误的根本原因吗？

调试 1：

考虑到null 的可能性，我尝试（徒劳）如下：

//  ps.setString(1, employee.getEmp_name());
//  ps.setString(2, employee.getLocation());
//  ps.setString(3, employee.getEmail());
//  ps.setString(4, employee.getDob());
//  ps.setString(5, employee.getEmp_id());

ps.setString(1, "Superman");
ps.setString(2, "Sky");
ps.setString(3, "anymail@dooodle.com");
ps.setString(4, "1-1-0111");
ps.setString(5, "501");
ps.executeUpdate(updateSql);

但仍然显示相同的输出。

Answer 1

逐行验证后，我发现以下行有错误：

ps.executeUpdate(updateSql);

结论：在这种情况下，executeUpdate() 是必需的，没有传递任何参数

官方文档：

int executeUpdate() throws SQLException

Executes the SQL statement in this PreparedStatement object, which must be an SQL Data Manipulation Language (DML) statement, such as INSERT, UPDATE or DELETE; or an SQL statement that returns nothing, such as a DDL statement.

Returns:
either (1) the row count for SQL Data Manipulation Language (DML) statements or (2) 0 for SQL statements that return nothing

Answer 2

我通常会做的是：

private static final String UPDATE_ITEM =
        "UPDATE `EMPLOYEE_INFO` SET emp_name=?, location=?, email=?, dob=? WHERE emp_id=?";

public void updateEmployeeDetails(Employee employee) {

    Connection conn = null;
    PreparedStatement ps = null;

    try {

        conn = JDBCUtility.getConnection();
        ps = conn.prepareStatement(UPDATE_ITEM);
        ps.setString(1, employee.getEmp_name()); /*all the attributes of employee object are of type String */
        ps.setString(2, employee.getLocation());
        ps.setString(3, employee.getEmail());
        ps.setString(4, employee.getDob());
        ps.setString(5, employee.getEmp_id());
        ps.executeUpdate();

    } catch (SQLException e) {
        System.out.println(e.getErrorCode());
        e.printStackTrace();
    }
}

但是你能仔细检查一下 employee.getEmp_name() 的返回值吗？