c-treeDB API for C++ - Developers Guide

CTField::SetFieldDefaultValue

Sets the field default value.

Declaration

void CTField::SetFieldDefaultValue(const CTString& value);

void CTField::SetFieldDefaultValue(pTEXT value, VRLEN length);

Description

value is a string with the default value. No checks are made to make sure the default value matches the correct field type. The caller is responsible for passing the appropriate value.
length is the length of string. You must pass a proper length of the string.

CTField::SetFieldDefaultValue() sets the field default value. The default value of a field is used during an alter table operation when a full table rebuild is performed. During a full alter table rebuild, and after the old record buffer data is moved to the new record buffer, the new record buffer is scanned and if a NULL field is found and that NULL field has a default value, the default value is copied to the field buffer.

The field default value is kept as a string representation of the data. It is recommended that numeric data should be converted to string using one of the rich set of c-treeDB data conversion functions.

Date values should be converted to string using the default date type value. The default date type value can be retrieved by calling CTField::GetFieldDefaultDateType() method. By default, the date type is CTDATE_MDCY.

Time values should be converted to string using the default time type value. The default time type value can be retrieved by calling CTField::GetFieldDefaultTimeType() function. By default, the time type is CTTIME_HMS.

Time stamp values should be converted to string using the default date type and time type values as described above.

Return

void

Example

// set the default value of country field */

try

{

CTField hField = hTable.GetField("country"));

hField.SetFieldDefaultValue("USA");

}

catch (CTException &err)

{

printf("SetFieldDefaultValue failed\n");

}