**Table 3-10: DirectConnect datatype conversions for alter table**
Adaptive Server datatype	DirectConnect default datatype
binary(n)	binary(n)
bit	bit
char	char
date	date
datetime	datetime
decimal(p, s)	decimal(p, s)
float	float
image	image
int	int
money	money
numeric(p, s)	numeric(p, s)
nchar(n)	nchar(n)
nvarchar(n)	nvarchar(n)
real	real
smalldatetime	smalldatetime
smallint	smallint
smallmoney	smallmoney
time	time
timestamp	timestamp
tinyint	tinyint
text	text
unichar	unichar
unitext	unitext
varbinary(n)	varbinary(n)
varchar(n)	varchar(n)

alter table

Server class ASEnterprise

Component Integration Services forwards the following syntax to a server configured as class ASEnterprise:

alter table [database.[owner].]table_name 
	{add column_name datatype [{identity | null}]
       {[, next_column]}...}
	| [drop column_name [, column_name]}
	| modify column_name [data_type] [NULL] | 
		[not null]] [, column_name]}

When a user adds a column with the alter table command, Component Integration Services passes the datatype of each column to the remote server without type name conversions.
For ASEnterprise class servers only, the lock clause is also forwarded, if contained in the original query, if the version of Adaptive Server is 11.9.2 or later.

Server class ASAnywhere

Handling of alter table by servers in this class is the same as for ASEnterprise servers.

Server class ASIQ

Handling of alter table by servers in this class is the same as for ASEnterprise servers.
text and image datatypes are fully supported by server class ASIQ.

Server class direct_connect

Component Integration Services forwards the following syntax to a remote server configured as class direct_connect:

alter table [database.[owner].]table_name 
 add column_name datatype [{identity | null}]
        {[, next_column]}...

Although Component Integration Services requests a capabilities response from a server with class direct_connect, support for alter table is not optional. Component Integration Services forwards alter table to the remote server regardless of the capabilities response.

The behavior of the server with class direct_connect is database dependent. The Transact-SQL syntax is forwarded, and errors may or may not be raised, depending on the ability of the remote database to handle this syntax.

Server class direct_connect does not support bigint, unsigned tinyint, unsigned smallint, unsigned int, unsigned bigint.

If the syntax capability of the remote server indicates Sybase Transact-SQL, Adaptive Server datatypes are sent to the remote server. If the syntax capability indicates DB2 SQL, DB2 datatypes are sent.

Direct Connect does not support bigint, unsigned tinyint, unsigned smallint, unsigned int, unsigned bigint.

The mapping for these datatypes is shown in Table 3-10:

Table 3-10: DirectConnect datatype conversions for alter table
Adaptive Server datatype

DirectConnect default datatype

binary(n)

binary(n)

bit

bit

char

char

date

date

datetime

datetime

decimal(p, s)

decimal(p, s)

float

float

image

image

int

int

money

money

numeric(p, s)

numeric(p, s)

nchar(n)

nchar(n)

nvarchar(n)

nvarchar(n)

real

real

smalldatetime

smalldatetime

smallint

smallint

smallmoney

smallmoney

time

time

timestamp

timestamp

tinyint

tinyint

text

text

unichar

unichar

unitext

unitext

varbinary(n)

varbinary(n)

varchar(n)

varchar(n)

Useage

When the server receives the alter table command, it passes the command to an appropriate access method if:

The object on which the command is to operate has been associated with a remote or external storage location.
The command consists of an add column request. Requests to add or drop constraints are not passed to the access methods; instead, they are handled locally.

alter table is passed to remote servers as a language request.