如何联接来自多个SQL查询的结果

Question

我希望显示在SELECT中定义的必需列，一旦执行了一个条件并打印了该条件的结果，我希望从SELECT的新指定列中显示另一个where子句，依此类推，首先，我需要为了解决这两个查询，该计划是与大约10个查询器混合使用。 感谢Ps的问题之一，所有结果都显示在i_di1.naziv列中

SELECT bolnickiracun.id,
         bolnickiracun.id_dijagnoza1, i_di1.naziv naziv_dijagnoza1
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di1 ON bolnickiracun.id_dijagnoza1=i_di1.id
WHERE  bolnickiracun.id_dijagnoza1!="" and i_di1.naziv is null
UNION ALL
SELECT bolnickiracun.id,
         bolnickiracun.id_dijagnoza2, i_di2.naziv naziv_dijagnoza2
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di2 ON bolnickiracun.id_dijagnoza2=i_di2.id
WHERE  bolnickiracun.id_dijagnoza2!="" and i_di2.naziv is null

我希望结果看起来像这样：

id id_dijagnoza1   naziv_dijagnoza1   id_dijagnoza2   naziv_dijagnoza2
1     some data         null             
2     some data         null
3                                        some data         null
4                                        some data         null

关键是要找到naziv_dijagnoza1或naziv_dijagnoza2，其中null为空，即外键显示不存在主键，或者有人导入了不作为主键存在的不良外键。

Answer 1

这个3个SELECT的示例（第三个示例是根据可以看到的模式通过推导预测的）应该有助于理解您需要对10个SELECT的整个查询执行的操作。 您需要填写与NULL SELECT子句后，每列你在每一个dont'need的SELECT 。

SELECT bolnickiracun.id, bolnickiracun.id_dijagnoza1, i_di1.naziv naziv_dijagnoza1, NULL, NULL, NULL, NULL -- and so on
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di1 ON bolnickiracun.id_dijagnoza1=i_di1.id
WHERE  bolnickiracun.id_dijagnoza1!="" and i_di1.naziv is null

UNION ALL

SELECT bolnickiracun.id, NULL, NULL, bolnickiracun.id_dijagnoza2, i_di2.naziv naziv_dijagnoza2, NULL, NULL -- and so on
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di2 ON bolnickiracun.id_dijagnoza2=i_di2.id
WHERE  bolnickiracun.id_dijagnoza2!="" and i_di2.naziv is null

UNION ALL

SELECT bolnickiracun.id, NULL, NULL, NULL, NULL, bolnickiracun.id_dijagnoza3, i_di3.naziv naziv_dijagnoza3 -- and so on
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di3 ON bolnickiracun.id_dijagnoza3=i_di3.id
WHERE  bolnickiracun.id_dijagnoza3!="" and i_di3.naziv is null

每个SELECT的列数应该相同，并且正如您所看到的，对于3 SELECT来说，它是7列（每个表连接2个x 3 SELECT s + 1个ID为ID的第一列）。 对于10个SELECT ，每个SELECT子句中将有21列（id为1列，在每个表中为2列，其余部分由NULL填充）。 这不是很好的解决方案，但可能仅具有这样的数据库结构。

因此，对于10 SELECT ，第一个和最后一个应该看起来像这样：

    SELECT bolnickiracun.id, bolnickiracun.id_dijagnoza1, i_di1.naziv naziv_dijagnoza1, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di1 ON bolnickiracun.id_dijagnoza1=i_di1.id
WHERE  bolnickiracun.id_dijagnoza1!="" and i_di1.naziv is null

UNION ALL
...
UNION ALL

SELECT bolnickiracun.id, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, bolnickiracun.id_dijagnoza10, i_di10.naziv naziv_dijagnoza10
FROM     bolnickiracun
LEFT JOIN i_dijagnoze_marko i_di10 ON bolnickiracun.id_dijagnoza10=i_di10.id
WHERE  bolnickiracun.id_dijagnoza10!="" and i_di10.naziv is null