create existing table

The preferred method of creating proxy tables is the create proxy_table command, which eliminates the need to define the column definitions.

Syntax

create existing table table_name (column_list) 
	[on segment_name]
	[[external {table | procedure | file | connection_type}] at pathname 
	[column delimiter "string"]]

Parameters

• table_name – specifies the name of the table for which you want to create a proxy table.
• column_list – specifies the name of the column list that stores information about the remote table.
• on segment_name – specifies the segment that contains the remote table.
• external – specifies that the object is a remote object.
• table – specifies that the remote object is a table or a view. The default is external table.
• procedure – specifies that the remote object is a stored procedure.
• file – specifies that the remote object is a file.
• connection_type – determines whether a remote procedure call uses the current or a separate connection. The valid values are:

  • non_transactional – is a separate connection is used to execute the RPC.

  • transactional – is the existing connection is used to execute the RPC.

  The default behavior is transactional.

• at pathname – specifies the location of the remote object. pathname takes the form: server_name.dbname.owner.object, where:

  • server_name (required) – is the name of the server that contains the remote object.

  • dbname (optional) – is the name of the database managed by the remote server that contains this object.

  • owner (optional) – is the name of the remote server user that owns the remote object.

  • object (required) – is the name of the remote table, view, or procedure.

• column delimiter – used to separate fields within each record when accesssing flat files. The column delimiter can be up to 16 bytes long.
• string – the column delimiter string can be any character sequencer, but if the string is longer than 16 bytes, only the first 16 bytes are used. The use of column delimiter for proxy tables mapped to anything but files results in a syntax error.

Examples

• Example 1 – Creates the proxy table authors:

  create existing table authors
  (
  au_id       id,
  au_lname    varchar (40)    NOT NULL,
  au_fname    varchar (20)    NOT NULL,
  phone       char (12),
  address     varchar (40)    NULL,
  city        varchar (20)    NULL,
  state       char (2)        NULL,
  zip         char (5)        NULL,
  contract    bit
  )
  at "nhserver.pubs2.dbo.authors"

• Example 2 – Creates the proxy table syb_columns:

  create existing table syb_columns
  (
  id        int,
  number    smallint,
  colid     tinyint,
  status    tinyint,
  type      tinyint,
  length    tinyint,
  offset    smallint,
  usertype  smallint,
  cdefault  int,
  domain    int,
  name      varchar (30),
  printfmt  varchar (255)    NULL,
  prec      tinyint         NULL,
  scale     tinyint         NULL
  )
  at "remote1.master.dbo.columns"

• Example 3 – Creates a proxy table named blurbs for the blurbs table at the remote server SERVER_A:

  create existing table blurbs
  (
  author_id      id      not null,
  copy           text    not null
  )
  at "SERVER_A.db1.joe.blurbs"

• Example 4 – Creates a proxy table named rpc1 for the remote procedure named p1:

  create existing table rpc1
  (
  column_1       int,
  column_2       int
  )
  external procedure
  at "SERVER_A.db1.joe.p1"

Usage

• create existing table does not create a new table unless the remote object is a file. Instead, CIS checks the table mapping to confirm that the information in column_list matches the remote table, verifies the existence of the underlying object, and retrieves and stores metadata about the remote table.

• If the host data file or remote server object does not exist, the command is rejected with an error message.

• If the object exists, the system tables sysobjects, syscolumns, and sysindexes are updated. The verification operation requires these steps:

  1. The nature of the existing object is determined. For host data files, this requires determining file organization and record format. For remote server objects, this requires determining whether the object is a table, a view, or an RPC.

  2. For remote server objects (other than RPCs), column attributes obtained for the table or view are compared with those defined in the column_list.

  3. Index information from the host data file or remote server table is extracted and used to create rows for the sysindexes system table. This defines indexes and keys in the SAP ASE server terms and enables the query optimizer to consider any indexes that might exist on this table.

• The on segment_name clause is processed locally and is not passed to a remote server.

• After successfully defining an existing table, issue update statistics for the table. This allows the query optimizer to make intelligent choices regarding index selection and join order.

• CIS allows you to create a proxy table with a column defined as NOT NULL even though the remote column is defined as NULL. It displays a warning to notify you of the mismatch.

• The location information provided by the at keyword is the same information that is provided by sp_addobjectdef. The information is stored in the sysattributes table.

• CIS inserts or updates a record in the systabstats catalog for each index of the remote table. Since detailed structural statistics are irrelevant for remote indexes, only a minimum number of columns are set in the systabstats record—id, indid, and rowcnt.

• External files cannot be of datatypes text, image, or Java ADTs.

Standards

ANSI SQL – Compliance level: Transact-SQL extension.

Permissions

create existing table permission defaults to the table owner and is not transferable.