Difference between revisions of "Using Navigational Data Access Commands in Recital"

Revision as of 10:40, 7 January 2010

Using Navigational Data Access Commands in Recital

Why use Navigational Data Access Commands

Creating a Recital Database

The create database command is used to create a new database. This will create a sub-directory in the DB_DATADIR directory and a database catalog with the same name as the database specified.

create database [if not exists] <database>

A database, its tables and other associated files can be physically deleted using the drop database command.

drop database [if exists] <database>

Example

create database test
drop database test

Opening a Recital Database

To open a database and set it as the default database for any subsequent operations, use the open database command.

open database <database> [EXCLUSIVE | SHARED] [NOUPDATE] [VALIDATE]

The open database command triggers the DBC_OPENDATA database event. If a dbc_opendata.prg program file exists in the database's directory, this will be run. If the dbc_opendata.prg program returns .F. (False), the open database operation will be abandoned.

Databases can also have an associated procedure library that is activated automatically when the database is opened. The procedure library must follow the naming convention dbc_<database>_library.prg and must exist in the database's directory. When the database is closed, the procedure library is also closed.

open database southwind

Creating a Recital Table

Tables can be created using the SQL create table statement. For full details, please see Using Recital SQL.

The copy command can be used to copy all or part of an active table to a new table. The records to be copied can be restricted using for and while conditions.

copy to <filename> [<scope>] [fields <field list>] [for <condition>] [while <condition>] 

use example order account_no
copy to new;
  fields account_no, last_name;
  while account_no < "00050";
  for state = "MA"

The copy structure command allows the entire structure or selected fields from an existing active table to be copied to a new table.

copy structure to <tablename> [fields <field list>] 

• CREATE
• CREATE FROM
• COPY STRUCTURE EXTENDED

Opening a Recital Table

• SELECT
• SELECT()
• USE

Navigating a Recital Table

• GOTO
• GOTO()
• INDEX
• REINDEX
• SEEK
• SEEK()
• SKIP

Inserting Records into a Recital Table

• APPEND FROM
• BLANK
• GATHER
• GENERATE
• REPLACE

Updating Records in a Recital Table

• GATHER
• REPLACE

Selecting Records from a Recital Table

• AVERAGE
• COUNT
• DISPLAY
• LIST
• SCAN
• SCATTER
• SUM
• TOTAL

Adding Records to a Recital Table

• APPEND
• APPEND BLANK
• INSERT

Deleting Records in a Recital Table

The deletion of records in a Recital table is a two stage process. The delete command is used to mark a record for deletion. At this stage, the marked record is hidden if set deleted is on. With set deleted set to off, the record is still accessible as normal. Record lists (list and display) will show the deletion marker * next to the record number and the deleted() function will return .T. (true). A record marked for deletion can have the mark removed using the recall command.

delete [<scope>][for | while <condition as logical>] 

recall [<scope>][for | while <condition as logical>] 

set deleted on | off 

set deleted off
use example
goto 10
delete
echo deleted() // .T.
recall
echo deleted() // .F.

To physically remove records marked for deletion, the pack command must be issued on the table. The table must be open for exclusive use.

use example exclusive
pack

The zap command can be used to physically delete all the records from a table immediately. The table must be open for exclusive use.

use example exclusive
zap

Obtain Information about a Recital Table

• DISPLAY/LIST STRUCTURE
• DISPLAY/LIST INDEX
• DISPLAY/LIST

• BOF()
• EOF()
• FIELD()
• FIELDNAME()
• FLDLIST()
• INUSE()
• RECNO()
• REFERENCES()
• USED()