Question

数据库MySQL的

以下是create table语句。

CREATE TABLE `Test`( `T` varchar(40) DEFAULT NULL,`P` varchar(40) NOT NULL,`CT` char(1) DEFAULT 'V',`XY` char(1) DEFAULT 'A');

在上表中有3列（T，P，CT，XY）。 1.在专栏＆＃39; T＆＃39;和专栏＆＃39; P＆＃39;具有这样的关系，即两列的值将成对。该对中的任何值都不会与其他列的其他值配对。 2.列CT有3种可能的值---＆gt; V，W，X。 3.列XY具有3种可能的值---＆gt; A，B，C。

表中的数据如下。

1. insert into Test values('T1','P1','V','A');
2. insert into Test values('T1','P2','V','B');
3. insert into Test values('T2','P3','V','C');
4. insert into Test values('T3','P3','V','A');
5. insert into Test values('T4','P4','V','A');
6. insert into Test values('T4','P4','V','A');
7. insert into Test values('T4','P4','V','B');
8. insert into Test values('T4','P4','W','A');
9. insert into Test values('T4','P4','X','A');

输出只有一行 - T4，P4,2

解释

1. First row will be discarded because of T1 is making pair with 2 values(P1,P2)of Column 'P'.
2. Second row will be discarded because of T1 is making pair with 2 values(P1,P2)of Column 'P'.
3. Third row will be discarded because of P3 is making pair with 2 values(T2,T3)of Column 'T'.
4. Fourth row will be discarded because of P3 is making pair with 2 values(T2,T3)of Column 'T'.
5. Output will be pair of T4,P4

对于一对（T4，P4），将导出第三列输出，计算列＆＃39; CT＆＃39;的实例数。值为V，列为＆＃39; XY＆＃39;值为A.有2个实例（你可以在第5行和第6行看到），所以输出的第3列将是2.

我尝试使用查询，但它没有给我正确的结果。

select T,P,sum from (select T,P,sum(if(CT = 'A' and XY = 'B',1,0)) sum from Test group by T,P ) X group by T having count(*)=1;

什么是Sql Query来解决上述问题？

Answer 1

通过使用汇总查询来查找和排除T或P在所有独特组合中重复的情况，可以满足您对输出生成方式的解释中的前四项。 T和P，就像在此处的子查询中所做的那样：

select
    t.T, t.P, count(*) as rows
from
    Test as t
    left join (
        select T from (select distinct T, P from Test) as p1 group by T having count(*) > 1
        ) as dupT on dupT.T=t.T
    left join (
        select P from (select distinct T, P from Test) as p2 group by P having count(*) > 1
        ) as dupP on dupP.P=t.P
where
    dupT.T is null
    and dupP.P is null
    and CT = 'V'
    and XY = 'A'
group by
    t.T, t.P;

这是对您的标准的完全字面解释，丢弃不良数据，但您也可以通过包含仅包含好数据来实现这一点：

select
    t.T, t.P, count(*) as rows
from
    Test as t
    inner join (
        select T from (select distinct T, P from Test) as p1 group by T having count(*) = 1
        ) as dupT on dupT.T=t.T
    inner join (
        select P from (select distinct T, P from Test) as p2 group by P having count(*) = 1
        ) as dupP on dupP.P=t.P
where
    CT = 'V'
    and XY = 'A'
group by
    t.T, t.P;

复杂的sqlQuery

1 个答案: