SELECT ProductName FROM Product where ProductId = 1012SELECT ColumnName FROM ProductMapping该语句的结果是"ProductName“
SELECT (SELECT PM.ColumName FROM Product where ProductId = 1012) FROM ProductMappin
我是sql数据库的初学者,我需要一些帮助....我有两个表(families_table )和(children_table ),它们通过family_id关联,所以家庭表中的每个家庭在孩子表中都有许多孩子……我想从族表中选择一些家庭,并知道所有选择的家庭的子代数量。我试着这样做
selectcount (*) from dbo.Children where family_id in (select top 50 percent * from dbo