大佬教程收集整理的这篇文章主要介绍了CASE语句是否会丢失PostgreSQL中的别名范围？，大佬教程大佬觉得挺不错的，现在分享给大家，也给大家做个参考。
SELEct case when s.luserID > 0 then u.szusername when s.lgroupID > 0 then g.szgroup when s.lldAPId > 0 then 'LDAP Group' end as name from security s left join users u on s.luserID = u.id left join usergroups g on s.lgroupID = g.ID order by name@H_@R_197_11404@_5@上面的块通过别名工作证明排序,以及声明别名名称有效,而术语名称是保留字,这与问题无关 @H_@R_197_11404@_5@当我在其中创建带有别名的case语句时,我的问题就出现了： @H_@R_197_11404@_5@注意别名usEID @H_@R_197_11404@_5@
SELEct case when sa.luserID > 0 then sa.luserID when sa.lgroupID > 0 then sa.lgroupID when sa.lldAPId > 0 then sa.lldAPId end as usEID,from security s left join users u on s.luserID = u.id left join usergroups g on s.lgroupID = g.ID order by case when 'user SELEction' = 'all objects by user' then usEID else s.lobjectID end@H_@R_197_11404@_5@在运行sql之前,文本用户选择由具有文字文本的解析器替换.别名usEID和s.lobjectID都是bigint类型. @H_@R_197_11404@_5@当’用户选择’=’用户的所有对象’然后使用usEID时,会引发错误. @H_@R_197_11404@_5@我是否在CASE声明中丢失了别名usEID的范围？
SELEct case when s.luserID > 0 then u.szusername when s.lgroupID > 0 then g.szgroup when s.lldAPId > 0 then 'LDAP Group' end as name from security s left join users u on s.luserID = u.id left join usergroups g on s.lgroupID = g.ID order by case when s.lobjectID > 0 then s.lobjectID else s.luserID end@H_@R_197_11404@_5@上面的块证明了ORDER BY语句中的CASE语句确实有效.关于上述sql块的逻辑操作的所有争论都与问题无关,因为它只是垃圾示例sql.
SELEct usEID,lobjectID from ( SELEct case when sa.luserID > 0 then sa.luserID when sa.lgroupID > 0 then sa.lgroupID when sa.lldAPId > 0 then sa.lldAPId end as usEID,lobjectID from security s left join users u on s.luserID = u.id left join usergroups g on s.lgroupID = g.ID ) as t order by case when 'user SELEction' = 'all objects by user' then usEID else lobjectID end@H_@R_197_11404@_5@或者你可以重复entiry case块 @H_@R_197_11404@_5@
SELEct case when sa.luserID > 0 then sa.luserID when sa.lgroupID > 0 then sa.lgroupID when sa.lldAPId > 0 then sa.lldAPId end as usEID,lobjectID from security s left join users u on s.luserID = u.id left join usergroups g on s.lgroupID = g.ID order by case when 'user SELEction' = 'all objects by user' then case when sa.luserID > 0 then sa.luserID when sa.lgroupID > 0 then sa.lgroupID when sa.lldAPId > 0 then sa.lldAPId end else lobjectID end@H_@R_197_11404@_5@某些引擎会让您使用选择范围上的字段的订单号,顺序如下： @H_@R_197_11404@_5@
SELEct a,b,c from sometable order by 1,2@H_@R_197_11404@_5@这意味着此查询将按字段a和b排序
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