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Shape APPEND Clause

  • Άρθρο

The shape command APPEND clause appends a column or columns to a Recordset. Frequently, these columns are chapter columns, which refer to a child Recordset.

Syntax

SHAPE [parent-command [[AS] parent-alias]] APPEND column-list

Description

The parts of this clause are as follows:

parent-command
Zero or one of the following (you can omit the parent-command completely):

  • A provider command enclosed in braces ("{}") that returns a Recordset object. The command is issued to the underlying data provider, and its syntax depends on the requirements of that provider. This will typically be the SQL language, although ADO does not require any particular query language.

  • Another shape command embedded in parentheses.

  • The TABLE keyword, followed by the name of a table in the data provider.

parent-alias
An optional alias that refers to the parent Recordset.

column-list
One or more of the following:

  • An aggregate column.

  • A calculated column.

  • A new column created by using the NEW clause.

  • A chapter column. A chapter column definition is enclosed in parentheses ("()"). See the following syntax.

SHAPE [parent-command [[AS] parent-alias]]  
   APPEND (child-recordset [ [[AS] child-alias]   
      RELATE parent-column TO child-column | PARAMETER param-number, ... ])  
   [[AS] chapter-alias]   
   [, ... ]

Remarks

child-recordset

  • A provider command enclosed in braces ("{}") that returns a Recordset object. The command is issued to the underlying data provider, and its syntax depends on the requirements of that provider. This will typically be the SQL language, although ADO does not require any particular query language.

  • Another shape command embedded in parentheses.

  • The name of an existing shaped Recordset.

  • The TABLE keyword, followed by the name of a table in the data provider.

child-alias
An alias that refers to the child Recordset.

parent-column
A column in the Recordset returned by the parent-command.

child-column
A column in the Recordset returned by the child-command.

param-number
See Operation of Parameterized Commands.

chapter-alias
An alias that refers to the chapter column appended to the parent.

Note

The "parent-column TO child-column" clause is actually a list, where each relation defined is separated by a comma

Note

The clause after the APPEND keyword is actually a list, where each clause is separated by a comma and defines another column to be appended to the parent.

When you construct provider commands from user input as part of a SHAPE command, SHAPE will treat the user-supplied a provider command as an opaque string and pass them faithfully to the provider. For example, in the following SHAPE command,

SHAPE {select * from t1} APPEND ({select * from t2} RELATE k1 TO k2)

SHAPE will execute two commands: select * from t1 and (select * from t2 RELATE k1 TO k2). If the user supplies a compound command that consists of multiple provider commands separated by semicolons, SHAPE is not able to distinguish the difference. So in the following SHAPE command,

SHAPE {select * from t1; drop table t1} APPEND ({select * from t2} RELATE k1 TO k2)

SHAPE executes select * from t1; drop table t1 and (select * from t2 RELATE k1 TO k2), not realizing that drop table t1 is a separate and in this case, dangerous, provider command. Applications must always validate the user input to prevent such potential hacker attacks from occurring.

This section contains the following topics.

See Also

Data Shaping Example
Formal Shape Grammar
Shape Commands in General