Question

我有一个数据库，其中有一个表有3列。这是.schema给出的： .schema

CREATE TABLE Frequency (
docid VARCHAR(255),
term VARCHAR(255),
count int,
PRIMARY KEY(docid, term));

我正在尝试连接查询以获取两个特定的docid并按术语匹配它们（对不起，如果它没有意义，我是sql的新手）。我期待的格式为：

docid1 |term |count
docid2 |term |count

同时尝试选择docid或任何其他列而不是执行select *会给我一个模糊的键错误。这是我正在使用的查询：

 select* from (select docid, term, count from frequency where docid = '10080_txt_crude') as c join (select docid , term, count from frequency where docid = '17035_txt_earn') as d on c.term = d.term;

最后，最后通过docid添加group只能给出一个答案。

Answer 1

SELECT docid,term,count
FROM Frequency
WHERE docid=docid1 or docid=docid2
GROUP BY docid,term,count
HAVING COUNT(*) >1

Answer 2

尝试select c.* from ...选择一个表中的所有列，而不是所有已连接表中的所有列。

select c.* from 
    (select docid, term, count from frequency where docid = '10080_txt_crude') as c 
join 
    (select docid , term, count from frequency where docid = '17035_txt_earn') as d 
on c.term = d.term;

或者，您可以进一步简化语法吗？

select c.docid,c.term,c.ount 
from frequency c
join frequency d on c.term = d.term
where c.docid = '10080_txt_crude' and
    d.docid = '17035_txt_earn';

问题是，你在哪里实际使用D.

您是否尝试select * from frequency where docid='10080_txt_crude' or docid='17035_txt_earn'？

加入两个DocID之间的匹配条款：

select c.docid as c_docid, d.docid as d_docid, c.term, c.count, d.count
from frequency c
join frequency d on c.term = d.term
where c.docid = '10080_txt_crude' and
    d.docid = '17035_txt_earn';

这将产生（C DocID，D DocID，Term （在C和D中相等），C Count，D Count）。

sql3查询，无法理解我做错了什么

2 个答案: