Question

我陷入两难境地，我希望有人能够帮助我。我试图从我的旧教科书中解决一些问题，这不是书中的问题，但数据是，我只是想看看我是否还可以在SQL中工作，所以这里是。执行此代码时，

SELECT COUNT(code_description) "Number of Different Crimes", last, first, 
code_description 
FROM
(
SELECT criminal_id, last, first, crime_code, code_description
FROM criminals 
JOIN crimes USING (criminal_id)
JOIN crime_charges USING (crime_id)
JOIN crime_codes USING (crime_code)
ORDER BY criminal_id
)
WHERE criminal_id = 1020
GROUP BY last, first, code_description;

我得到了这些结果：

Number of Different Crimes   LAST            FIRST      CODE_DESCRIPTION             
                     1       Phelps          Sam        Agg Assault                    
                     1       Phelps          Sam        Drug Offense

不可避免地，我希望每一行的不同罪行数量为2，因为这名罪犯有两项独特的罪行。我希望它显示如下：

Number of Different Crimes   LAST            FIRST      CODE_DESCRIPTION             
                     2       Phelps          Sam        Agg Assault                    
                     2       Phelps          Sam        Drug Offense

不是为了我的运气，但我也想摆脱以下行：

WHERE criminal_id = 1020

以更优雅的方式代表任何与他们相关的犯罪类型超过1的犯罪分子，对于这种情况，Sam Phelps是此数据集中唯一的一个。

Answer 1

正如@sgeddes在评论中所说的那样，您可以使用分析计数，如果您指定了犯罪ID，则不需要子查询：

SELECT COUNT(code_description) OVER (PARTITION BY first, last) AS "Number of Different Crimes",
  last, first, code_description 
FROM criminals 
JOIN crimes USING (criminal_id)
JOIN crime_charges USING (crime_id)
JOIN crime_codes USING (crime_code)
WHERE criminal_id = 1020;

如果你想寻找有多种罪行的人，那么你需要一个子查询，这样你就可以过滤分析结果：

SELECT charge_count AS "Number of Different Crimes",
  last, first, code_description
FROM (
  SELECT COUNT(DISTINCT code_description) OVER (PARTITION BY first, last) AS charge_count,
    criminal_id, last, first, code_description 
  FROM criminals 
  JOIN crimes USING (criminal_id)
  JOIN crime_charges USING (crime_id)
  JOIN crime_codes USING (crime_code)
)
WHERE charge_count > 1
ORDER BY criminal_id, code_description;

SQL Fiddle demo

如果指控涉及多个犯罪，但重复，那么非重复计数仍然有效，但您可能希望为整体结果集添加一个独特的 - 除非您想显示其他犯罪特定信息 - 否则您{ {3}}

具有不同计数的SQL嵌套查询

1 个答案: