Column Index Element

Function:

Specifies a column as an index.

Invocation:

This element is part of the table column element.

Syntax:

column_index_element.bmp
 

index_identifier

A valid identifier for an index conforming to the rules described in the section Identifiers.

Description:

The following conventions hold true for the following explanations:

  • Let C be the column for which this column index element is specified.

  • Let T be the table where column C resides.

INDEX:

If there is no range specified in an INDEX specification an Adabas descriptor will be added. If a range is specified across only one column, an Adabas Subdescriptor will be generated.

 

HAVING UNIQUE INDEX:

This feature is provided for compatibility and will be removed in future versions. Use the UNIQUE constraint instead.

 

UQINDEX:

A UQINDEX is an index that generates an Adabas unique sub- or superdescriptor on a subtable column. SQL does not consider this descriptor to be unique so it cannot be represented by a normal "unique constraint."

 

Limitations:

  • A HAVING UNIQUE INDEX specification is not allowed in subtables. A UQINDEX specification is allowed in subtables.

  • Do not specify a HAVING UNIQUE INDEX together with a UNIQUE constraint or a PRIMARY KEY.

  • HAVING UNIQUE INDEX cannot have both the NOT NULL and the SUPPRESSION attributes.

  • HAVING UNIQUE INDEX cannot have both the NULL and the Adabas DEFAULT attributes.

ANSI Specifics:

The Column Index Element is not part of the Standard.

Adabas SQL Gateway Embedded SQL Specifics:

None.