使用NOT EXISTS 对LOV进行控制

需求：当选择一个任务的成员或者客户时候，要使LOV只显示在数据库表中未插入的数据。

        

解决办法： 应用对LOV的数据源进行控制。采用NOT EXISTS

 

代码如下：

SELECT all_data.project_id project_id, all_data.task_id task_id, all_data.customer_id customer_id, all_data.task_customer_name task_customer_name, all_data.task_customer_number task_customer_number, all_data.project_relationship_code project_relationship_code, all_data.record_version_number record_version_number, all_data.bill_to_customer_id bill_to_customer_id, all_data.bill_customer_name bill_customer_name, all_data.bill_customer_number bill_customer_number, all_data.bill_to_address_id bill_to_address_id, all_data.bill_address1 bill_address1, all_data.bill_address2 bill_address2, all_data.bill_address3 bill_address3, all_data.bill_address4 bill_address4, all_data.ship_to_customer_id ship_to_customer_id, all_data.ship_customer_name ship_customer_name, all_data.ship_customer_number ship_customer_number, all_data.ship_to_address_id ship_to_address_id, all_data.ship_address1 ship_address1, all_data.ship_address2 ship_address2, all_data.ship_address3 ship_address3, all_data.ship_address4 ship_address4 FROM (SELECT ppc.project_id project_id, pt.task_id task_id, ppc.customer_id customer_id, hp.party_name task_customer_name , hp.party_number task_customer_number, ppc.project_relationship_code project_relationship_code, ppc.record_version_number record_version_number, ppc.bill_to_customer_id bill_to_customer_id, hp.party_name bill_customer_name, hp.party_number bill_customer_number, ppc.bill_to_address_id bill_to_address_id, bill_loc.address1 bill_address1, bill_loc.address2 bill_address2, bill_loc.address3 bill_address3, bill_loc.address4 || DECODE(bill_loc.address4, NULL, NULL, ', ') || bill_loc.city || ' , ' || NVL(bill_loc.state, bill_loc.province) || ' ' || bill_loc.postal_code || ' , ' || bill_loc.county bill_address4, ppc.ship_to_customer_id ship_to_customer_id, hp.party_name ship_customer_name, hp.party_number ship_customer_number, ppc.ship_to_address_id ship_to_address_id, ship_loc.address1 ship_address1, ship_loc.address2 ship_address2, ship_loc.address3 ship_address3, ship_loc.address4 || DECODE(ship_loc.address4, NULL, NULL, ', ') || ship_loc.city || ' , ' || NVL(ship_loc.state, ship_loc.province) || ' ' || ship_loc.postal_code || ' , ' || ship_loc.county ship_address4 FROM pa_project_customers ppc, hz_parties hp, hz_cust_accounts hca, hz_cust_acct_sites_all bill_site, hz_cust_acct_sites_all ship_site, hz_party_sites bill_party_site, hz_party_sites ship_party_site, hz_locations bill_loc, hz_locations ship_loc, pa_tasks pt WHERE hp.party_id = hca.party_id AND hca.cust_account_id = ppc.customer_id AND ppc.bill_to_customer_id = bill_site.cust_account_id AND ppc.bill_to_address_id = bill_site.cust_acct_site_id(+) AND ppc.ship_to_customer_id = ship_site.cust_account_id AND ppc.ship_to_address_id = ship_site.cust_acct_site_id(+) AND hp.party_id = bill_party_site.party_id AND hp.party_id = ship_party_site.party_id AND bill_site.party_site_id = bill_party_site.party_site_id(+) AND ship_site.party_site_id = ship_party_site.party_site_id(+) AND bill_party_site.location_id = bill_loc.location_id(+) AND ship_party_site.location_id = ship_loc.location_id(+) AND pt.project_id = ppc.project_id) all_data WHERE NOT EXISTS (SELECT tc.project_id, tc.task_id, tc.customer_id FROM cux_pa_task_customers tc WHERE all_data.project_id = tc.project_id AND all_data.task_id = tc.task_id AND all_data.customer_id = tc.customer_id) AND all_data.project_id=:PARAMETER.G_PROJECT_ID AND all_data.task_id =:PARAMETER.G_TASK_ID

 

 oracle中的exists和not exists和in用法:
有两个简单例子，以说明 “exists”和“in”的效率问题

　　1) select * from T1 where exists(select 1 from T2 where T1.a=T2.a) ;

　　T1数据量小而T2数据量非常大时，T1<<T2 时，1) 的查询效率高。

　　2) select * from T1 where T1.a in (select T2.a from T2) ;

　　T1数据量非常大而T2数据量小时，T1>>T2 时，2) 的查询效率高。

　　exists 用法：

　　请注意 1）句中的有颜色字体的部分 ，理解其含义；

　　其中 “select 1 from T2 where T1.a=T2.a” 相当于一个关联表查询，相当于

　　“select 1 from T1,T2 where T1.a=T2.a”

　　但是，如果你当当执行 1） 句括号里的语句，是会报语法错误的，这也是使用exists需要注意的地方。

　　“exists（xxx）”就表示括号里的语句能不能查出记录，它要查的记录是否存在。

　　因此“select 1”这里的 “1”其实是无关紧要的，换成“*”也没问题，它只在乎括号里的数据能不能查找出来，是否存在这样的记录，如果存在，这 1） 句的where 条件成立。

　　in 的用法：

　　继续引用上面的例子

　　“2) select * from T1 where T1.a in (select T2.a from T2) ”

　　这里的“in”后面括号里的语句搜索出来的字段的内容一定要相对应，一般来说，T1和T2这两个表的a字段表达的意义应该是一样的，否则这样查没什么意义。

　　打个比方：T1，T2表都有一个字段，表示工单号，但是T1表示工单号的字段名叫“ticketid”，T2则为“id”，但是其表达的意义是一样的，而且数据格式也是一样的。这时，用 2）的写法就可以这样：

　　“select * from T1 where T1.ticketid in (select T2.id from T2) ”

　　Select name from employee where name not in (select name from student);

　　Select name from employee where not exists (select name from student);

　　第一句SQL语句的执行效率不如第二句。

　　通过使用EXISTS，Oracle会首先检查主查询，然后运行子查询直到它找到第一个匹配项，这就节省了时间。Oracle在执行IN子查询时，首先执行子查询，并将获得的结果列表存放在一个加了索引的临时表中。在执行子查询之前，系统先将主查询挂起，待子查询执行完毕，存放在临时表中以后再执行主查询。这也就是使用EXISTS比使用IN通常查询速度快的原因