C5_CREATE FROM

 CREATE FROM
 Create a new .dbf file from a structure extended file
------------------------------------------------------------------------------
 Syntax

     CREATE <xcDatabase> FROM <xcExtendedDatabase> [NEW]
        [ALIAS <xcAlias>] [VIA <cDriver>]

 Arguments

     <xcDatabase> is the name of the new database file to create from the
     structure extended file.

     <xcExtendedDatabase> is the name of a structure extended file to use
     as the structure definition for the new database file.

     Both of these arguments can be specified either as literal database file
     names or as character expressions enclosed in parentheses.  If an
     extension is not specified, the default is .dbf.

     NEW opens <xcDatabase> in the next available work area making it
     the current work area.  If this clause is not specified, <xcDatabase> is
     opened in the current work area.

     ALIAS <xcAlias> is the name to associate with the work area when
     <xcDatabase> is opened.  You may specify the alias name as a literal
     name or as a character expression enclosed in parentheses.  A valid
     <xcAlias> may be any legal identifier (i.e., it must begin with an
     alphabetic character and may contain numeric or alphabetic characters
     and the underscore).  Within a single application, Clipper will not
     accept duplicate aliases.  If this clause is not specified, the alias
     defaults to the database file name.

     VIA <cDriver>  specifies the replaceable database driver (RDD) to
     use to process the current work area.  <cDriver> is the name of the RDD
     specified as a character expression.  If you specify <cDriver> as a
     literal value, you must enclose it in quotes.

 Description

     CREATE FROM produces a new database file with the field definitions
     taken from the contents of a structure extended file.  To qualify as a
     structure extended file, a database file must contain the following four
     fields:

     Structure of an Extended File
     ------------------------------------------------------------------------
     Field   Name           Type        Length    Decimals
     ------------------------------------------------------------------------
     1       Field_name     Character   10
     2       Field_type     Character   1
     3       Field_len      Numeric     3         0
     4       Field_dec      Numeric     4         0
     ------------------------------------------------------------------------

     <xcDatabase> is automatically opened in the current work area after it
     is created.

 Notes

     .  Data dictionaries: For data dictionary applications, you can
        have any number of other fields within the structure extended file to
        describe the extended field attributes.  You may, for example, want
        to have fields to describe such field attributes as a description,
        key flag, label, color, picture, and a validation expression for the
        VALID clause.  When you CREATE FROM, Clipper creates the new
        database file from the required fields only, ignoring all other
        fields in the extended structure.  Moreover, Clipper is not
        sensitive to the order of the required fields.

     .  Character field lengths greater than 255: There is one method
        for creating a character field with a length greater than 255 digits:

        -  Specify the field length using both the Field_len and
           Field_dec fields according to the following formulation:

           FIELD->Field_len := <nFieldLength> % 256
           FIELD->Field_dec := INT(<nFieldLength> / 256)

 Examples

     .  This example is a procedure that simulates an interactive
        CREATE utility:

        CreateDatabase("NewFile")
        RETURN

        FUNCTION CreateDatabase( cNewDbf )
           CREATE TmpExt          // Create empty structure extended
           USE TmpExt
           lMore := .T.
           DO WHILE lMore         // Input new field definitions
              APPEND BLANK
              CLEAR
              @ 5, 0 SAY "Name.....: " GET Field_name
              @ 6, 0 SAY "Type.....: " GET Field_type
              @ 7, 0 SAY "Length...: " GET Field_len
              @ 8, 0 SAY "Decimals.: " GET Field_dec
              READ
              lMore := (!EMPTY(Field_name))
           ENDDO

           // Remove all blank records
           DELETE ALL FOR EMPTY(Field_name)
           PACK
           CLOSE

           // Create new database file
           CREATE (cNewDbf) FROM TmpExt
           ERASE TmpExt.dbf
           RETURN NIL

     .  This example creates a new definition in a structure extended
        file for a character field with a length of 4000 characters:

        APPEND BLANK
        REPLACE Field_name WITH "Notes",;
           Field_type WITH "C",;
           Field_len  WITH 4000 % 256,;
           Field_dec  WITH INT(4000 / 256)

 Files   Library is CLIPPER.LIB.

See Also: COPY STRUCTURE COPY STRU EXTE CREATE



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2 responses to “C5_CREATE FROM

  1. Pingback: DB Commands | Viva Clipper !

  2. Pingback: C5 Commands | Viva Clipper !

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