__dbCreate()

Template

Function

Name

__dbCreate()

Category

API

Subcategory

Database

Oneliner

Create structure extended file or use one to create new file

Syntax

      __dbCreate( <cFileName>,  [<cFileFrom>],  [<cRDDName>],  ;
                  [<lNew>],  [<cAlias>] ) --> lUsed

Arguments

<cFileName> is the target file name to create and then open. (.dbf) is the default extension if none is given.

<cFileFrom> is an optional structure extended file name from which the target file <cFileName> is going to be built. If omitted, a new empty structure extended file with the name <cFileName> is created and opened in the current work-area.

<cRDDName> is RDD name to create target with. If omitted, the default RDD is used.

<lNew> is an optional logical expression, (.T.) opens the target file name <cFileName> in the next available unused work-area and makes it the current work-area. (.F.) opens the target file in the current
work-area. Default value is (.F.). The value of <lNew> is ignored if <cFileFrom> is not specified.

<cAlias> is an optional alias to USE the target file with. If not specified, alias is based on the root name of <cFileName>.

Returns

__dbCreate() returns (.T.) if there is database USED in the current work-area (this might be the newly selected work-area), or (.F.) if there is no database USED. Note that on success a (.T.) would be returned, but on failure you probably end up with a run-time error and not a (.F.) value.

Description

__dbCreate() works in two modes depending on the value of <cFileFrom>:

1) If <cFileFrom> is empty or not specified a new empty structure extended file with the name <cFileName> is created and then opened in the current work-area (<lNew> is ignored). The new
file has the following structure:

       Field name   Type   Length   Decimals
       ----------   ----   ------   --------
       FIELD_NAME   C      10        0
       FIELD_TYPE   C       1        0
       FIELD_LEN    N       3        0
       FIELD_DEC    N       3        0

The CREATE command is preprocessed into the __dbCopyStruct() function during compile time and uses this mode.

2) If <cFileFrom> is specified, it is opened and assumed to be a structure extended file where each record contains at least the following fields (in no particular order): FIELD_NAME, FIELD_TYPE,
FIELD_LEN and FIELD_DEC. Any other field is ignored. From this information the file <cFileName> is then created and opened in the current or new work-area (according to <lNew>), if this is a new work-area it becomes the current.

For prehistoric compatibility reasons, structure extended file Character fields which are longer than 255 characters should be treated in a special way by writing part of the length in the FIELD_DEC according to the following formula:

      FIELD->FIELD_DEC := Int( nLength / 256 )
      FIELD->FIELD_LEN := ( nLength % 256 )

CREATE FROM command is preprocessed into __dbCopyStruct() function during compile time and use this mode.

Examples

      // CREATE a new structure extended file,  append some records and
      // then CREATE FROM this file a new database file

      __dbCreate( "template" )
      dbAppend()
      FIELD->FIELD_NAME := "CHANNEL"
      FIELD->FIELD_TYPE := "N"
      FIELD->FIELD_LEN  := 2
      FIELD->FIELD_DEC  := 0
      dbAppend()
      FIELD->FIELD_NAME := "PROGRAM"
      FIELD->FIELD_TYPE := "C"
      FIELD->FIELD_LEN  := 20
      FIELD->FIELD_DEC  := 0
      dbAppend()
      FIELD->FIELD_NAME := "REVIEW"
      FIELD->FIELD_TYPE := "C"      // this field is 1000 char long
      FIELD->FIELD_LEN  := 232      // 1000 % 256 = 232
      FIELD->FIELD_DEC  := 3        // 1000 / 256 = 3
      dbCloseArea()
      __dbCreate( "TV_Guide",  "template" )

Compliance

Clipper

Platforms

All

Files

Library is rdd

Seealso

COPY STRUCTURE, COPY STRUCTURE EXTENDED, CREATE, CREATE FROM, dbCreate(), dbStruct(), __dbCopyStruct(), __dbCopyXStruct()

3 responses to “__dbCreate()

  1. Pingback: Harbour Internal Functions | Viva Clipper !

  2. Pingback: Harbour Database Functions | Viva Clipper !

  3. Pingback: Harbour RG Summary | Viva Clipper !

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