Sybase Interview Questions and Answers

In my experience, many investment banks use Sybase as their database management system.


Q. How would you go about creating a new stored procedure in Sybase?
A. The basic steps involved are

1. Check if the procedure already exists?
2. If it already exists drop the procedure
3. create a new procedure with input arguments
4. declare any additional variables to be used in the procedure
5. assign values to these variables
6. create temporary tables and load some data
7. join other tables with temp tables to process data
8. handle error  scenarios
9. Keep track of the row counts
10. add logging statements where required.


Here is a very simplified example, covering a number of key aspects of a stored procedure.

-- select the schema to use
use my_db_schema 
go

IF OBJECT_ID('dbo.my_stored_proc') IS NOT NULL
BEGIN
    DROP PROCEDURE dbo.my_stored_proc
    IF OBJECT_ID('dbo.my_stored_proc') IS NOT NULL
        PRINT '<<< FAILED DROPPING PROCEDURE dbo.my_stored_proc >>>'
    ELSE
        PRINT '<<< DROPPED PROCEDURE dbo.my_stored_proc >>>'
END
go

CREATE PROC dbo.my_stored_proc  
(   
    @ParentName      varchar(30) = null,
    @ParentBatchJobId   int = null
)   
AS   

--declare variables
DECLARE @error  int,   
    @rowcount   int,   
    @error_message  varchar(240),  
 @error_number   int,
 @NumberOfDays   int,
 @DeleteDate datetime,
    @TotalRows  int,
 @proc_name  varchar(30),   
 @now        datetime
 
 
--assign values to your variables
  SELECT  @proc_name  = object_name(@@procid),
          @now     = GETDATE(),
    @rowcount     = 0,
          @TotalRows = 0

  
   select  @NumberOfDays = NumberValue,
           @DeleteDate = DateValue
        from    ConfigTable
        where   type = 'basic' and name='purge'
       
 -- error handling from last select
  SELECT @Error = @@Error   
        IF @Error <> 0
        BEGIN   
            SELECT @error_number = 50010
            SELECT @error_message = "Failed: could not get number of days parameter.(" + CONVERT(varchar(10), @Error) + ") "
            GOTO Error_Exit   
        END
 
 
 --Create a temporary table select the parant ids that need to be deleted
 CREATE TABLE #tmp_parent_ids
    (   
       ParentId    numeric(12,0)  not null
    )
    
    insert  into #tmp_parent_ids 
    select distinct(parent_id) from dbo.parent_table where createddttm < @DeleteDate
    
 
 
 if @NumberOfDays > 0
 BEGIN
 
   -- execute another stored proc and get an output to be used in this stored proc
    EXEC another_stored_proc "BatchJob", @NewNum = @ChildBatchJobId Output  

    SELECT @Error = @@Error   
       IF @Error <> 0 OR @ChildBatchJobId IS NULL   
       BEGIN   
         SELECT @error_number = 50050
         SELECT @error_message = "Failed: could not get the next BatchJobId from the SequenceNumber table.(" + CONVERT(varchar(10), @Error) + ") "
         GOTO Error_Exit   
        END    
  
  
  //do som logic like purging rows
    BEGIN   
           
            SET ROWCOUNT @PurgeRows   
       
            BEGIN TRANSACTION   

            DELETE child_table
            FROM child_table ct, #tmp_parent_ids tmp
            WHERE ct.parent_id = tmp.ParentId
       
            SELECT  @Error = @@Error, @Rows = @@Rowcount
            IF @Error != 0   
            BEGIN   
                SELECT @error_number = 50100
                SELECT @error_message = "Failed: (" + CONVERT(varchar(10), @Error) + ") could delete rows"
                ROLLBACK TRANSACTION       
                GOTO Error_Exit   
            END   
 
 END
 

success_exit:
      RETURN (0)
 
Error_Exit:  

     SELECT @error_message = "Error processing the proc" + " " + + @error_message;
  RAISERROR @error_number @error_message   
     RETURN (1)
  
go

IF OBJECT_ID('dbo.my_stored_proc') IS NOT NULL
    EXEC sp_procxmode 'dbo.my_stored_proc','unchained'
go
IF OBJECT_ID('dbo.my_stored_proc') IS NOT NULL
    PRINT '<<< CREATED PROCEDURE dbo.my_stored_proc >>>'
ELSE
    PRINT '<<< FAILED CREATING PROCEDURE dbo.my_stored_proc >>>'
go
IF OBJECT_ID('dbo.my_stored_proc') IS NOT NULL
    GRANT EXECUTE ON dbo.my_stored_proc TO user_admin
go

@@variable_name like @@Error, @@procid are Sybase variables. @variable_name like @Error are user defined stored proc variables.