Open statement [Revelation On-Line Wiki]

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====== Open statement   ======


 
==== Description ====
 
Creates a table access variable (a file handle).
 
==== Syntax ====
 
**Open**["DICT",] //expression// To //table_var// Then  Else //statements//
 
==== Parameters ====
 
The Open statement has the following parameters.

^Parameter^Description^
|//expression//|Designates the native table that is to be opened. To open the dictionary, use DICT as the first part of the table name (example: "DICT.CUSTOMERS"); and to open the data portion of the table, use only the table name (example: "CUSTOMERS"). Use separate Open statements to open the DICT and data portions of each table.|
|//table_var//|After a successful Open operation, //table_var// contains information about the table. From that point on, refer to the table with //table_var//, not with the actual table name.|
|Then|The statement(s) following Then are executed if a table is opened successfully.|
|Else|The statement(s) following Else are executed if the table cannot be opened. The [[status|Status()]] function indicates the severity of the error, and the system variable [[Table_Access#@FILE_ERROR|@FILE_ERROR]] contains detail about the nature of the error.\\ |
\\ You must Open a table before attempting to [[read|Read]] or [[write|Write]] rows from/to that table. As long as a table has been opened once, it does not need to be opened again each time you want to Read or Write to it.\\ \\ Each table must be opened with a separate Open statement. Any number of tables may be opened at any point in the program.\\ \\ Tables opened with the Open command need not and cannot be closed.|

 
==== See Also ====
 
[[index.open|Index.Open subroutine]], [[attach_table|Attach_Table]]
 
==== Example ====
 
<code>
/* The following program demonstrates file opening and subsequent processing. */

table = "CAR_PARTS"

Open table To tablevar Then
  Open "DICT", table To @DICT Else null
End Else
  * error processing:  cannot open table
End
Select tablevar
Done = 0
Printer On
Loop
  ReadNext @ID Else done = 1
 Until done
  Read @RECORD From tablevar, @ID Then
    report = {PART_NAME}:" ":{PART_TYPE}:" ":{PART_NO}
    Print report
  End
Repeat
Printer Off
</code>