tsql - Case 语句中的 RAISERROR

Question

能否不在 T-SQL 的 case 语句中引发错误？我总是遇到 SQL case 语句的问题:/

    begin try
    declare @i int 
    --set @i = (select COUNT(1) from table_name)

    select Item_Num =
        CASE (select COUNT(1) from table_name)
            when 1 then (select Item_Num from table_name)
            when 0 then (raiserror('No records in database', 0, 0))
            ELSE (raiserror('Multiple records in database', 0, 0))
        END
    from table_name

    end try
    begin catch
        declare @errormsg nvarchar(1024),
                @severity int,
                @errorstate int;

        select @errormsg = error_message(),
                @severity = error_severity(),
                @errorstate = error_state();

        raiserror(@errormsg, @severity, @errorstate);
    end catch

Answer 1

将 Case/When 视为对单个数据的操作。如果你这样想，很多问题就会迎刃而解。

If/Then 用于控制逻辑流程。

这样的东西应该适合你。

declare @i int 
set @i = (select COUNT(1) from table_name)

If @i = 1
  Begin
    Print "1 row"
  End
Else If @i = 0
  Begin
    Print "no rows"
  End
Else
  Begin
    Print "too many rows"
  End