ORACLE- CASE需要INTO吗？

Question

When I try the following:

declare var_type VARCHAR2(10);

begin

  var_type := 'B';

  select case var_type 
           when 'B' then 'Beans' 
           when 'L' then 'Legumes' 
         end 
    from tableOfBeans ;

end;

I get an error saying

ORA-06550: line 4, column 1:
PLS-00428: an INTO clause is expected in this SELECT statement
Error detected at position #:62

But when I don't use var_type but instead use 'B' as the condition it works nicely. Can anyone tell me why this happens and how do I fix it so I can use var_type properly?

Answer 1

You have wrapped your SQL in a begin/end block, which makes it a PL-SQL statement. In PL-SQL, Oracle is expecting a place to put the result set from the SQL. That's the source of your ORA-06550 error. You'll want a PL-SQL variable declared to hold the result of the query via the INTO.

But the SELECT statement is still a little weird. The way you have it, there's no point in having a real table "tableOfBeans" in the FROM clause.

Did you want something like this?

declare var_type VARCHAR2(10);

begin

    select case tableOfBeans.beanType
               when 'B' then 'Beans'
               when 'L' then 'Legumes'
           end
      into var_type
      from tableOfBeans;

end;

Actually, that would generate an error too if you had more than one row in tableOfBeans. Maybe what you wanted was to retrieve items from tableOfBeans where tableOfBeans.beanType = var_type. In that case you'd still need a way to store the result set. Sorry if I'm not understanding what you're trying to do. A little more detail will help.

Answer 2

The CASE statement doesn't require an INTO .
ORA-6550 is a generic error for when your SQL doesn't compile. The error is reporting that it thinks the issue is there's no INTO clause because it thinks you're trying to perform a SELECT INTO statement, like this:

SELECT t.column
  INTO var_type
  FROM tableOfBeans

I don't have an Oracle install to test against, but I have experienced Oracle 9i/10g being weird with CASE statements, sometimes requiring you to use END CASE rather than just END . END CASE is mentioned in the Oracle documentation here .

Usually you'd use DUAL for this sort of thing, testing if the variable is set:

var_type := 'B';

SELECT CASE var_type 
         WHEN 'B' then 'Beans' 
         WHEN 'L' then 'Legumes' 
       END CASE
  FROM DUAL;

Answer 3

As answered before the errors says that you have to put the result of the select into a variable.

declare 
    var_type VARCHAR2(10);
    var_into VARCHAR2(10);
begin
    var_type := 'B';

    select case var_type 
           when 'B' then 'Beans'
           when 'L' then 'Legumes'
    end
    into var_into
    from tableOfBeans;
end;

If your table tableOfBeans contains more than one row you will run into another error ORA-01422: exact fetch returns more than one row. Use pseudo table dual instead or following pl/sql code.

declare 
    var_type VARCHAR2(10);
    var_into VARCHAR2(10);
begin
    var_type := 'B';

    var_into := case var_type 
           when 'B' then 'Beans'
           when 'L' then 'Legumes'
    end;
end;