MySQL 数据库错误：操作数应包含 1 列
这是声明。目的并不重要，只是我需要能够判断发布规则属于什么类型的对象。谢谢！
select case(select count(mediaitemguid) from mediaitempublicationrules where publicationruleguid = '<snip>')
when 0 then case(select count(catalogguid) from catalogpublicationrules where publicationruleguid = '<snip>')
when 0 then case(select count(domainguid) from domaindefaultpublicationrules where publicationruleguid = '<snip>')
when 0 then null
else (select 'Domain', domainguid from domaindefaultpublicationrules where publicationruleguid = '<snip>')
end
else (select 'Catalog', catalogguid from catalogpublicationrules where publicationruleguid = '<snip>')
end
else (select 'MediaItem', mediaitemguid from mediaitempublicationrules where publicationruleguid = '<snip>')
end;
编辑：更多的澄清...这工作得很好，直到我将这些“域”“目录”“媒体项”条目放入 else 语句的嵌套选择中。这可能相当简单，只是之前没有遇到过这个错误
Here is the statement. The purpose isn't really important, just that I need to be able to tell what type of object the publication rule belongs to. Thanks!
select case(select count(mediaitemguid) from mediaitempublicationrules where publicationruleguid = '<snip>')
when 0 then case(select count(catalogguid) from catalogpublicationrules where publicationruleguid = '<snip>')
when 0 then case(select count(domainguid) from domaindefaultpublicationrules where publicationruleguid = '<snip>')
when 0 then null
else (select 'Domain', domainguid from domaindefaultpublicationrules where publicationruleguid = '<snip>')
end
else (select 'Catalog', catalogguid from catalogpublicationrules where publicationruleguid = '<snip>')
end
else (select 'MediaItem', mediaitemguid from mediaitempublicationrules where publicationruleguid = '<snip>')
end;
EDIT: a little more clarification...this worked just fine until I put those 'Domain' 'Catalog' 'MediaItem' entries into the nested selects on the else statements. It's probably something fairly simple, just haven't run into that error before
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该错误表明您应该返回单列而不是两列
解决方法之一是使用
concat_ws类似The error indicate you should return single column instead of two
One way to fix is to use
concat_wslike