java - 如果其中一个字段可能为空，如何更新表中的多个字段？

Question

我想在名为 Personnel-table 的表中更新用户个人信息的 5 字段。

用户可能想要更新所有字段、部分字段或根本不更新任何字段。

用户可能想要更新的字段是:FirstName、LastName、Password、UserName 和地址 .

该代码执行此操作:

public boolean updateUserInfo(String _idnumber , String _usernameNew , String _passwordNew ,  
        String _addressNew , String _firstNameNew , String _lastNameNew) throws SQLException
{

    ResultSet resultSet = null;

    String sqlStatement = "UPDATE PersonnelTable set `UserName` = ? WHERE `IdNumber` = ?";
    this.m_prepared = (PreparedStatement) this.m_connection.prepareStatement(sqlStatement);
    this.m_prepared.executeUpdate("USE Personnel");

    // set the ID number & account number 


    /**
     *  first 
     */
    m_prepared.setString(1, _usernameNew);
    m_prepared.setString(2, _idnumber);

    // execute first query - update password
    if (_usernameNew!= "")
    {
        resultSet = m_prepared.executeQuery();
        return true;
    }

    /**
     *  Second 
     */

    sqlStatement = "UPDATE PersonnelTable set `FirstName` = ? WHERE `IdNumber` = ?";
    this.m_prepared = (PreparedStatement) this.m_connection.prepareStatement(sqlStatement);
    m_prepared.setString(1, _firstNameNew);
    m_prepared.setString(2, _idnumber);

    if (_firstNameNew != "")
    {
        resultSet = m_prepared.executeQuery();
        return true;
    }


    /**
     *  Third
     */

    sqlStatement = "UPDATE PersonnelTable set `LastName` = ? WHERE `IdNumber` = ?";
    this.m_prepared = (PreparedStatement) this.m_connection.prepareStatement(sqlStatement);
    m_prepared.setString(1, _lastNameNew);
    m_prepared.setString(2, _idnumber);

    if (_lastNameNew!= "")
    {
        resultSet = m_prepared.executeQuery();
        return true;
    }

    /**
     *  Fourth
     */

    sqlStatement = "UPDATE PersonnelTable set `Address` = ? WHERE `IdNumber` = ?";
    this.m_prepared = (PreparedStatement) this.m_connection.prepareStatement(sqlStatement);
    m_prepared.setString(1, _addressNew);
    m_prepared.setString(2, _idnumber);

    if (_addressNew!= "")
    {
        resultSet = m_prepared.executeQuery();
        return true;
    }



    /**
     *  Fifth
     */

    sqlStatement = "UPDATE PersonnelTable set `Password` = ? WHERE `IdNumber` = ?";
    this.m_prepared = (PreparedStatement) this.m_connection.prepareStatement(sqlStatement);
    m_prepared.setString(1, _passwordNew);
    m_prepared.setString(2, _idnumber);

    if (_passwordNew!= "")
    {
        resultSet = m_prepared.executeQuery();
        return true;
    }



    return false;
} 

但如您所见，代码太大，因为我运行了 5 次查询。

如何告诉 mysql 如果每个字段都不是空字符串 "" ，然后更新需要的字段，在一个 mysql 查询中？这是可能的还是我必须每次都单独做？

问候

Answer 1

您可以在单个查询中轻松地执行此操作:

UPDATE PersonnelTable
SET FirstName = IF(? <> "", ?, FirstName),
    LastName = IF(? <> "", ?, LastName),
    Password = IF(? <> "", ?, Password),
    UserName = IF(? <> "", ?, UserName),
    Address = IF(? <> "", ?, Address)
WHERE IdNumber = ?;

如果您的字段可以有空白值，例如 ""，那么您可以使用 IF(? IS NOT NULL, ?, field_name) 而不是空白。