部件功能模块代码学习

oracle在where子句中加(+) 

Oracle数据库的连接查询包括：等值连接、外连接、自连接等。
where子句中加(+) 是外连接的一种。外连接分：左外连接和右外连接。
select * from emp,dept where emp.deptno=dept.deptno(+); --右外连接
select * from emp,dept where emp.deptno(+)=dept.deptno; --左外连接

带(+)侧的数据即使不存在，另一侧的数据依然可以显示出来。

delete数据时sql语句编写

在拼接字符串时，删除语句使用where(1!=1)防止没有参数传值导致的sql语句出错

  @Override
    public void delete(List<DcDevice> list) throws ApplicationException {
            StringBuffer masterHqlBf = new StringBuffer();
        StringBuffer detailHqlBf = new StringBuffer();
        masterHqlBf.append(" delete from DcDevice where (1 != 1) ");
        detailHqlBf.append(" delete from DcDeviceAttachment where (1 != 1) ");

        for (Iterator<DcDevice> it = list.iterator(); it.hasNext();) {
            DcDevice dcDevice = it.next();
            masterHqlBf.append(" or (deviceId = '");
            masterHqlBf.append(dcDevice.getDeviceId());
            masterHqlBf.append("') ");
            detailHqlBf.append(" or (dcDevice.deviceId = '");
            detailHqlBf.append(dcDevice.getDeviceId());
            detailHqlBf.append("') ");
        }
        try {
                  execHqlUpdate(detailHqlBf.toString());
                  execHqlUpdate(masterHqlBf.toString());
        } catch (OPException ex) {
            throw new ApplicationException("删除设备失败！", ex);
        }
    }