Question

我有两个表ward1和ward2ie;

create table ward1
(
ward_id int
)

create table ward2
(
ward_id int,
ward_name varchar(10)
)

，值为 -

insert into ward1 values(101);
insert into ward1 values(101);
insert into ward1 values(102);
insert into ward1 values(102);
insert into ward1 values(102);

insert into ward2 values(101,'child');
insert into ward2 values(102,'General');

所以我需要产生ward_id的总发生次数。对我来说这很简单，我使用了这段代码。

SELECT ward_id, count(ward_id) as "No of occurrence" from ward1 group by ward_id;

输出是 -

ward_id   No of occurrence
101       2
102       3

这是来自ward1表的记录，但是当我需要来自表ward2的ward_name时。我收到了错误。这是我的代码 -

select ward1.ward_id as "ward_id",ward2.ward_name,
count(ward1.ward_id)as "No of occurrence" from ward1,
ward2 group by ward1.ward_id,ward2.ward_name 
having ward1.ward_id=ward2.ward_id;

它不是表达群体......

我想这样显示 -

ward_id   ward_name    No of occurrence
101       child        2
102       General      3

请帮忙......

Answer 1

关闭。您真的只需要在where子句中加入2个表（或使用首选的“join”语句）

select ward1.ward_id as "ward_id",ward2.ward_name,
count(ward1.ward_id)as "No of occurrence" 
from ward1,ward2 
where ward1.ward_id = ward2.ward_id
group by ward1.ward_id,ward2.ward_name;

Answer 2

您不需要HAVING子句，只需使用WHERE子句链接表格：

select ward1.ward_id as "ward_id",
       ward2.ward_name,
       count(ward1.ward_id) as "No of occurrence" 
  from ward1,
       ward2
 WHERE ward1.ward_id = ward2.ward_id
 group by ward1.ward_id,
          ward2.ward_name;

您应该使用SQL-92语法而不是SQL-86，然后只需要添加JOIN条件：

select ward_id,
       ward2.ward_name,
       count(ward_id) as "No of occurrence" 
  from ward1
 INNER JOIN ward2 USING (ward_id)
 group by ward_id,
          ward2.ward_name;

希望它有所帮助...

Answer 3

select ward1.ward_id as "ward_id",
       ward2.ward_name,
       count(ward1.ward_id) as "No of occurrence"
from   ward1, ward2
where  ward1.ward_id = ward2.ward_id
group by ward1.ward_id,ward2.ward_name;

如何在oracle中使用group by子句合并两个表中的记录？

3 个答案: