public class SysUser extends BaseEntity
{
    private static final long serialVersionUID = 1L;
    
    private Long userId;
    private Long deptId;
    private String userName;
    private String nickName;
    private String email;
    ......
}

public interface SysUserMapper
{
    public List<SysUser> selectUserList(SysUser sysUser);
    public SysUser selectUserByUserName(String userName);
    public SysUser selectUserById(Long userId);
    public int insertUser(SysUser user);
    ......
}

<mapper namespace="com.ruoyi.project.system.mapper.SysUserMapper">

<insert id="insertUser" parameterType="SysUser" useGeneratedKeys="true" keyProperty="userId">
    insert into sys_user(
        <if test="userId != null and userId != 0">user_id,</if>
        <if test="deptId != null and deptId != 0">dept_id,</if>
        <if test="userName != null and userName != ''">user_name,</if>
        <if test="nickName != null and nickName != ''">nick_name,</if>
        <if test="email != null and email != ''">email,</if>
        create_time
    )values(
        <if test="userId != null and userId != ''">#{userId},</if>
        <if test="deptId != null and deptId != ''">#{deptId},</if>
        <if test="userName != null and userName != ''">#{userName},</if>
        <if test="nickName != null and nickName != ''">#{nickName},</if>
        <if test="email != null and email != ''">#{email},</if>
        sysdate()
    )
</insert>