Sybase Interview Questions and Answers

1 :: How do I tell which tables have identities in Sybase?

You can tell if a table has identities one of two ways:

1. sp_help [tablename]: there is a field included in the sp_help output describing a table called "Identity." It is set to 1 for identity fields, 0 otherwise.
2. Within a database, execute this query:

1. select object_name(id) "table",name "column", prec "precision"
2. from syscolumns
3. where convert(bit, (status & 0x80)) = 1
4. go

this will list all the tables and the field within the table that serves as an identity, and the size of the identity field.

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2 :: How do I Configure the burn factor in Sybase?

The number of identity values that gets "burned" upon a crash or a shutdown can by found by logging into the server and typing:
1.sp_configure "identity burning set factor"
2. go

the Default value set upon install is 5000. The number "5000" in this case is read as ".05% of all the potential identity values you can have in this particular case will be burned upon an unexpected shutdown." The actual number depends on the size of the identity field as you specified it when you created your table.

To set the burn factor, type:

1. sp_configure "identity burning set factor", [new value]
2. go

This is a static change; the server must be rebooted before it takes effect

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3 :: How do I configure Identities in Sybase?

You can either create your table initially with the identity column:

1. create table ident_test
2. (text_field varchar(10),
3. ident_field numeric(5,0) identity)
4. go


Or alter an existing table and add an identity column:

1. alter table existing_table
2. add new_identity_field numeric(7,0) identity
3. go


When you alter a table and add an identity column, the System locks the table while systematically incrementing and adding unique values to each row. IF YOU DON'T SPECIFY a precision, Sybase defaults the size to 18! Thats 1,000,000,000,000,000,000-1 possible values and some major major problems if you ever crash your ASE and burn a default number of values... (10^18 with the default burn factor will burn 5^14 or 500,000,000,000,000 values...yikes).

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4 :: How can I execute dynamic SQL with ASE in Sybase?

Adaptive Server Enterprise: System 12

ASE 12 supports dynamic SQL, allowing the following:

declare @sqlstring varchar(255)
select @sqlstring = "select count(*) from master..sysobjects"
exec (@sqlstring)
go


Adaptive Server Enterprise: 11.5 and 11.9

* Firstly define your local server to be a remote server using
sp_addserver LOCALSRV,sql_server[,INTERFACENAME]
go

* Enable CIS
sp_configure "enable cis",1
go

* Finally, use sp_remotesql, sending the sql to the server defined in point 1.
declare @sqlstring varchar(255)
select @sqlstring = "select count(*) from master..sysobjects"
sp_remotesql LOCALSRV,@sqlstring
go

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5 :: Which version of Open Client works with which ASE in Sybase?

The TDS protocol that *is* Open Client is built so that either the client or server will fallback to a common dialect. I suppose that it is theoretically possible that both would fallback for some reason, but it seems unlikely. I was recently working with a client that was using Open/Client 4.2 to speak to a version 11.5 ASE using Powerbuilder 3 and 4! Amazing, it all worked! The main problem that you will encounter is not lack of communication but lack of features. The facility to bcp out of views was added to the 11.1.1 release. You will still be able to connect to servers with old copies of Open/Client, you just won't have all of the features.

There is also another fairly neat feature of the later releases of Open/Client, it has a very good compatibility mode for working with old applications. The client that was running Open/Client 4.2 with Powerbuilder 3 is now connecting to the database using version 11.1.1. Which is not bad when you remember that Powerbuilder 3 only talked 4.2 DBLib!

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