Question

我正在使用SQLITE3 3.14.2并尝试执行以下操作：

给出两个表IP和lookem：

drop table IP;
create table IP(IP TEXT,
                Name TEXT);
insert into IP values('10.5.6.7','Joe');
insert into IP values('10.6.6.7','Joe');
insert into IP values('10.2.3.4','Frank');
insert into IP values('10.3.5.7','David');
insert into IP values('10.34.56.78','David');
--select * from IP;

drop table lookem;
create table lookem(IP TEXT,
                    Name TEXT);
insert into lookem values('','Joe');    -- Exclude Joe for All IPs
insert into lookem values('','George');  -- Exclude George for all IPs
insert into lookem values('10.4.5.6','Frank');-- Excl Frank for 1 ip
insert into lookem values('10.34.56.78','David');-- Excl David on Specific IP
--select * from lookem;

select a.ip,a.name,b.name,b.ip from lookem a join ip b on 
   (b.name like case when a.name='' then '%' else a.name end) and
   (b.ip   like case when a.ip=''   then '%' else a.ip   end);

以上选择正确地适用于我，显示lookem表与多个标准上的IP表匹配的所有情况，用通配符替换空值。

|Joe|Joe|10.5.6.7
|Joe|Joe|10.6.6.7
10.34.56.78|David|David|10.34.56.78

然而，相反的是什么？我真正需要的是对比赛的排除。换句话说，将返回一个查询：

10.3.5.7|David
10.2.3.4|Frank

唯一的结果。提前感谢您的帮助。

Answer 1

以下是使用NOT EXISTS

的一种方法

SELECT a.ip,
       a.NAME
FROM   IP a
WHERE  NOT EXISTS (SELECT 1
                   FROM   lookem b
                   WHERE  ( a.IP = b.ip
                             OR b.ip = '' )
                          AND a.NAME = b.NAME)

如果您想要使用lookem表格选择列，请使用Left JOIN

SELECT a.ip,
       a.NAME
FROM   IP a
       LEFT JOIN lookem b
              ON ( a.IP = b.ip
                    OR b.ip = '' )
                 AND a.NAME = b.NAME
WHERE  b.NAME IS NULL

您的第一个查询也可以使用EXISTS

重写

SELECT a.ip,
       a.NAME
FROM   IP a
WHERE   EXISTS (SELECT 1
                   FROM   lookem b
                   WHERE  ( a.IP = b.ip
                             OR b.ip = '' )
                          AND a.NAME = b.NAME)

如果您想要使用lookem表格选择列，请使用Inner JOIN

SELECT a.ip,
       a.NAME
FROM   IP a
       JOIN lookem b
         ON ( a.IP = b.ip
               OR b.ip = '' )
            AND a.NAME = b.NAME

如何根据表中的条件选择排除项

1 个答案: