The "subquery returns more than one value" issue in a federated query in SQL

In a subquery, if you want to implement the following functions:

Select Lib,count (*), select SUM (NEWSNO) from Table1 GROUP by Lib

From Tabel1 t1,table2 T2 where T1.newsno =t2.newsno

Group by Lib

You will be prompted that the subquery returns more than one value. "Error, meaning that a subquery cannot return multiple results, only one result can be returned.

Therefore, you can use the following method instead:

Select Lib,count (*), select SUM (newsno) from Table1 T1 where T1.lib =table1.lib

From Tabel1 t1,table2 T2 where T1.newsno =t2.newsno

Group by Lib

The reason is still not very understanding, but also need expert guidance, may be related to the execution order of an SQL statement

The "subquery returns more than one value" issue in a federated query in SQL