UPDATE

UPDATE

Update current database file from another database file

Syntax

      UPDATE FROM <xcAlias>
            ON <expKey> [RANDOM]
            REPLACE <idField> WITH <exp>
            [, <idField2> WITH    <exp2>...]

Arguments

FROM <xcAlias> specifies the alias of the work area used to update records in the current work area. This argument may be specified either as a literal file name or as a character expression enclosed in parentheses.

ON <expKey> specifies the expression that defines matching records in the FROM work area.

REPLACE <idField> specifies a field in the current work area to replace with a new value.

WITH <exp> specifies the value to replace into the current field. You must reference any field contained in the FROM work area with the correct alias.

RANDOM allows records in the FROM database file to be in any order. If this option is specified, the current database file must be indexed on <expKey>.

Description

UPDATE is a database command that replaces fields in the current work area with values from another work area based on the specified key expression. UPDATE is designed to update only current work area records based on a one-to-one or one-to-many relation with the FROM work area. This means that UPDATE can only update records in the current work area with unique key values. When there is more than one instance of a key value, only the first record with the key value is updated. The FROM work area, however, can have duplicate key values.

There are two formulations of the command depending on whether the FROM work area records are sorted or indexed on <expKey> or not. If RANDOM is not specified, both the current work area and the FROM work area must be indexed or sorted in <expKey> order. If RANDOM is specified, the current work area must be indexed by <expKey>, but the FROM work area records can be in any order.

To use UPDATE in a network environment, the current database file must be locked with FLOCK() or USEed EXCLUSIVEly. The FROM database file may be used in any mode. Refer to the “Network Programming” chapter in the Programming and Utilities Guide for more information.

Notes

. Deleted records: If DELETED is OFF, deleted records in both source files are processed. Records in the file being updated retain their deleted status and are not affected by the deleted status of records in the FROM file. If DELETED is ON, however, no deleted records are processed from either source file.

Examples

      .  This example UPDATEs the Customer database file with
         outstanding invoice amounts:

      USE Invoices NEW
      USE Customer INDEX Customer NEW
      UPDATE FROM Invoices ON Last;
         REPLACE Owed WITH Owed + Invoices->Amount RANDOM

Seealso

DBCREATEIND(), INDEX, JOIN, REPLACE, SET UNIQUE*, SORT

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