sql - 导致 PostgreSQL 9.3 中的语法错误的代码有什么问题

Question

下面是我写的一段 SQL 代码。我想将两条记录合并到一条记录中，其中第一条记录域显示为“来自源”，第二条记录的域变为“到域”。我需要做更多的过滤，但为什么这个简单的语句不起作用？

我收到错误“输入末尾的语法错误”

*SELECT 
   "ID" , "Time",  "Source Domain", "To Domain" From
   (SELECT "RecordID" As "ID","UTCTimestamp" As "Time","Domain" As "Source Domain" FROM public."Traffic - Mobile")T1
   Inner Join Lateral
   (SELECT "Domain" As "To Domain" FROM public."Traffic - Mobile" where "RespondentID"="T1"."RespondentID" )T2*

提前致谢

PostgreSQL 版本 9.3

Answer 1

我认为你过于复杂了。一个简单的表自连接就足够了。您不需要派生表来重命名列

SELECT "ID", "Time", t1."Domain" as "Source Domain", t2."Domain" as "To Domain" 
from public."Traffic - Mobile" as t1
  join public."Traffic - Mobile" as t2 on t2."RespondentID" = t1."RespondentID";

Answer 2

我认为您仍然需要一个ON子句，因为它是一个INNER JOIN. 如果您不想指定ON子句，我认为您可以CROSS JOIN改用。

例如

SELECT 
   "ID" , "Time",  "Source Domain", "To Domain" From
   (SELECT "RecordID" As "ID","UTCTimestamp" As "Time","Domain" As "Source Domain"
          FROM public."Traffic - Mobile")T1
   Inner Join Lateral
   (SELECT "Domain" As "To Domain" FROM public."Traffic - Mobile"
           where "RespondentID"="T1"."RespondentID" )T2
    ON true