Question

第一次查询：

select MONTHNAME(batchStartDate) AS MONTHS,
    MONTH(batchStartDate) AS MONTHNUMBER,
    SUM(totalCandidatesInBatch) AS CANDIDATES_ENROLLED 
from batch 
group by MONTHS 
order by MONTHNUMBER;

第二次查询：

select MONTHNAME(resultApprovedOndate) AS MONTHS,
    MONTH(resultApprovedOndate) AS MONTHNUMBER,
    SUM(totalCertified) AS CANDIDATES_CERTIFIED 
from batch 
where totalPass is not null AND 
    totalFail is not null AND 
    resultApprovedOnDate<=curDate() and 
    resultApprovedOnDate is not null 
group by MONTHS 
order by MONTHNUMBER;

第3次查询：

select MONTHNAME(assessmentDate) AS MONTHS,
    MONTH(assessmentDate) AS MONTHNUMBER,
    (SUM(totalPass)+SUM(totalFail)) AS CANDIDATES_ASSESSED 
from batch 
where totalPass is not null AND 
    totalFail is not null AND 
    resultApprovedOnDate<=curDate() and 
    resultApprovedOnDate is not null 
group by MONTHS 
order by MONTHNUMBER;

正如您所看到的，这些查询具有公共列MONTHS和MONTHNUMBER，我想加入这三个查询的结果。我尝试过UNION但是没有用。

任何人都可以告诉我发生了什么以及解决方案是什么？

OUTPUT 第一次查询

 # MONTHS, MONTHNUMBER, CANDIDATES_ENROLLED
 January,       1,       50
 February,      2,       35
 March,         3,       205
 April,         4,       85
 May,           5,       616
 June,          6,       26

第二次查询

 # MONTHS, MONTHNUMBER, CANDIDATES_CERTIFIED
  January,       1,            34
    April,       4,            72
     July,       7,            484
   August,       8,            30

第三次查询

 # MONTHS, MONTHNUMBER, CANDIDATES_ASSESSED
 February,       2,           101
    March,       3,           134
      May,       5,           32
     July,       7,           75
   August,       8,           75
September,       9,           150
  October,       10,           75
 November,       11,           77
 December,       12,          152

我希望输出以表格

显示

# MONTHS, MONTHNUMBER, CANDIDATES_ENROLLED, CANDIDATES_CERTIFIED, CANDIDATES_ASSESSED

并且如果一个表有一个行缺失，那么该值应该用零或null填充.Ex-在第三个查询输出中，1月缺失，那么评估的候选应该是0或null。

Answer 1

看看这个链接： https://www.w3schools.com/sql/sql_join.asp

它会显示不同类型的联接（我假设您想要进行＆＃34;加入＆＃34;）。

Union用于将两个或多个集合组合在一起。

使用联接，您可以根据表格之间的相关列加入

Answer 2

我认为这可以通过一个查询来完成：

select MONTHNAME(batchStartDate) AS `MONTHS`,
    MONTH(batchStartDate) AS `MONTHNUMBER`,
    SUM(totalCandidatesInBatch) AS `CANDIDATESE_ENROLLED`,
    SUM(
        IF(NOT(totalFail IS NULL) AND 
            NOT(totalFail IS NULL) AND 
            resultApprovedOnDate <= curDate() AND 
            NOT(resultApprovedOnDate is null),
            totalCertified,
            0
        ) AS `CANDIDATESE_CERTIFIED`,
    SUM(
        IF(NOT(totalFail IS NULL) AND 
            NOT(totalFail IS NULL) AND 
            resultApprovedOnDate <= curDate() AND 
            NOT(resultApprovedOnDate is null),
            totalPass + totalFail,
            0
        ) AS `CANDIDATESE_ASSESSED`
from batch 
group by MONTHS 
order by MONTHNUMBER;

如何加入具有公共列的三个不同的SQL查询

2 个答案: