SQL中的聚合函数

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我有三个表，我想要这个：对于每个技能，开始于2016年，并且是至少两个培训包的一部分，并且分数介于12和17之间，列出技能ID，其类别，其水平，作为其一部分的训练包数量及其平均得分。SQL中的聚合函数

我写了下面的代码，但当我选择avg和sum时出现问题。

select SKILLNUM , SKCATEGORY , SKLEVEL , count(TPID) 
from (trainingpack t join Is_part_of i on t.TPID=i.TPID join skill s on i.SKILLNUM=s.SKILLNUM) 
where STARTINGDATE like '%2016' and COMPLDATE is not null and score between 12 and 17 
and (SKILLNUM) in (
select is_part_of.SKILLNUM 
from is_part_of 
group by SKILLNUM 
having count(TPID) >=2);

而且我想这个代码

select SKILL.SKILLNUM , SKILL.SKCATEGORY , SKILL.SKLEVEL ,count(IS_PART_OF.TPID),sum(IS_PART_OF.SCORE) 
from SKILL,TRAININGPACK,IS_PART_OF 
where TRAININGPACK.STARTINGDATE like '%2016' and IS_PART_OF.COMPLDATE is not null and IS_PART_OF.score between 12 and 17 
and IS_PART_OF.TPID=TRAININGPACK.TPID and IS_PART_OF.SKILLNUM=SKILL.SKILLNUM and (is_part_of.SKILLNUM) in (
select is_part_of.SKILLNUM 
from is_part_of 
group by SKILLNUM 
having count(TPID) >=2);

来源

2016-12-24 omar alabdulwahab

显示示例表 – DCR

首先找出您正在使用的RDBMS。然后参见http://meta.stackoverflow.com/questions/333952/why-should-i-provide-an-mcve-for-what-seems-to-me-to-be-a-very-simple-sql-查询 – Strawberry

您可能需要在group by子句中添加其他列。所以GROUP BY SkillNum，SkCategory，SkLevel –

您可以使用aggregate functions没有group by一句话，只要你不包括你的SELECT子句中其他列。

例如：可以使用下面的句子select在您的查询，但你希望你不会得到通过SKILLNUM，SKCATEGORY和SKLEVEL报告..你将只能得到全球数和金额的结果：

select count(IS_PART_OF.TPID),sum(IS_PART_OF.SCORE) from ...

当你正在寻找通过SKILLNUM，SKCATEGORY和SKLEVEL的报告，你应该包括在您的查询的末尾group by条款：

... group by SKILL.SKILLNUM , SKILL.SKCATEGORY , SKILL.SKLEVEL

所以，不知道到底你的数据库模型，您的查询应该是：

select SKILL.SKILLNUM , SKILL.SKCATEGORY , SKILL.SKLEVEL ,count( IS_PART_OF.TPID),sum(IS_PART_OF.SCORE) 
from SKILL, TRAININGPACK, IS_PART_OF 
where TRAININGPACK.STARTINGDATE like '%2016' 
and IS_PART_OF.COMPLDATE is not null 
and IS_PART_OF.score between 12 and 17 
and IS_PART_OF.TPID = TRAININGPACK.TPID 
and IS_PART_OF.SKILLNUM = SKILL.SKILLNUM 
and is_part_of.SKILLNUM in (
select is_part_of.SKILLNUM 
from is_part_of 
group by SKILLNUM 
having count(TPID) >=2) 
group by SKILL.SKILLNUM , SKILL.SKCATEGORY , SKILL.SKLEVEL

来源

2016-12-24 23:14:52

SQL中的聚合函数

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