请大家帮忙分析这个句子

Question

一个子查询，一个连接~~~select 
a.FILE_ORDER,
a.FILE_NAME,
a.FILE_SIZE,
b.full_name as PROVIDER,
a.UPLOAD_DATE,
a.FILE_PATH,
a.NOTE 
from 
(
  select 
    FILE_ORDER,
    WEB_FOLDER+WORK_OBJECT_ID+FILE_NAME+isnull(LOCK,'false')+FILE_NAME as FILE_NAME,
    FILE_SIZE,
    PROVIDER,
    UPLOAD_DATE,
    FILE_PATH,
    NOTE 
  from AF_UPLOAD_FILE 
  where work_object_id='"+ workObjectID +"' 
)a,wf_reg_users b 
where UPPER(a.PROVIDER)=b.user_name_upcase

Answer 1

select a.FILE_ORDER,a.WEB_FOLDER+a.WORK_OBJECT_ID+a.FILE_NAME+isnull(a.LOCK,'false')+a.FILE_NAME as FILE_NAME,a.FILE_SIZE,b.full_name as PROVIDER,a.UPLOAD_DATE,a.FILE_PATH,a.NOTE from AF_UPLOAD_FILE a,wf_reg_users b where a.work_object_id='"+ workObjectID +"' and UPPER(a.PROVIDER)=b.user_name_upcase如果排序规则不是大小写敏感的，就没必要用 UPPER 函数，如下select a.FILE_ORDER,a.WEB_FOLDER+a.WORK_OBJECT_ID+a.FILE_NAME+isnull(a.LOCK,'false')+a.FILE_NAME as FILE_NAME,a.FILE_SIZE,b.full_name as PROVIDER,a.UPLOAD_DATE,a.FILE_PATH,a.NOTE from AF_UPLOAD_FILE a,wf_reg_users b where a.work_object_id='"+ workObjectID +"' and a.PROVIDER=b.user_name_upcase

Answer 2

select a.FILE_ORDER,a.FILE_NAME,a.FILE_SIZE,b.full_name as PROVIDER,a.UPLOAD_DATE,a.FILE_PATH,a.NOTE from 
(select FILE_ORDER,WEB_FOLDER+WORK_OBJECT_ID+FILE_NAME+isnull(LOCK,'false')+FILE_NAME as FILE_NAME,FILE_SIZE,PROVIDER,UPLOAD_DATE,FILE_PATH,NOTE from AF_UPLOAD_FILE where work_object_id='"+ workObjectID +"' ) a -----------看成一个表.
,wf_reg_users b 
where UPPER(a.PROVIDER)=b.user_name_upcase--------关联字段
UPPER---返回将小写字符数据转换为大写的字符表达式。