Interstage Shunsaku Data Manager Application Development Guide - Microsoft(R) Windows(R) 2000/ Microsoft(R) Windows Server(TM) 2003 - - UNIX -

B.4.3 Format Used when Aggregating

To aggregate data, specify text expressions, attribute expressions single-line function specifications, or aggregation function specifications in the return expression. Multiple specifications can be entered, each separated with commas. The return expression must include at least one aggregation function specification.

A sort expression must be specified when aggregating. Refer to B.5 Sort Expressions for more information on sort expressions.

• Data is first sorted according to the sort key specified by the text expressions, attribute expressions or single-line functions specified in the sort expression
• Data with the same sort key is treated as a single group
• The result of the aggregation function specification is determined for each group.

[Figure B-20 Format Used when Aggregating]

The return items are shown below.

• Text Expressions
• Attribute Expressions
• Single-line Function Specification
• Aggregation Function Specifications

Text Expressions

Specify a text expression when extracting a key for aggregation.

Refer to B.2.2 Text Expressions for more information on the format for text expressions.

• If a text expression is specified, it must be the same as the text expression used in the sort expression. The value used as the key for aggregation will be returned.

Example

/doc/company/employee/dept/text()

Attribute Expressions

An attribute expression is used for extracting the key for aggregation.

Refer to B.2.3 Attribute Expressions for more information on the format for attribute expressions.

• The '*' cannot be specified at the attribute name specified by the attribute expression.
• If an attribute expression is specified, it must be the same as the attribute expression used in the sort expression. The value used as the key for aggregation will be returned.

Example

/doc/company/employee/@position

Single-line Function Specification

Specify single-line functions and extract the value of them when using single-line function specifications as the key for aggregation.

Refer to B.2.4 Single-line Function Specification for more information on the format for single-line function specifications.

• If a single-line function is specified, it must be the same as the single-line function specification used in the sort expression. The value used as the key for aggregation will be returned.

Example 1

rlen(/doc/company/employee/name/text(),3)

Example 2

rlen(/doc/company/employee/@position,3)

Aggregation Function Specifications

Aggregation function specifications aggregate the values specified by the text expression or attribute expression passed as an argument.

The definition format for aggregation function specifications is shown below.

[Figure B-21 Aggregation Function Specification Definition]

• If the element node specified by the text expression or the attribute node specified by the attribute expression is not in the document, it will not be included in the aggregation target.
• If the value represented by the text expression or attribute expression specified as an argument to the aggregation function does not exist, it will not be included in the aggregation target.
• The avg, sum, max and min functions extract numeric values from the strings specified by the text expression or attribute expression and aggregate these values. The principles for extracting numeric values from text expressions or attribute expressions are the same as for the val single-line function specification.
• An error will occur if an aggregation function produces result data whose integer part exceeds 18 digits. However, no error will occur even if intermediate result data for an aggregation exceeds 18 digits.

The avg Function

Extracts only numeric values from the strings expressed by the text expression or attribute expression and determines the average of these values.

The sum Function

Extracts only numeric values from the strings expressed by the text expression or attribute expression and determines the sum of these values.

The max Function

Extracts only numeric values from the strings expressed by the text expression or attribute expression and determines the maximum of these values.

The min Function

Extracts only numeric values from the strings expressed by the text expression or attribute expression and determines the minimum of these values.

The count Function

Determines the number of elements specified by the text expression or attribute expression.

• The '//' path operator cannot be specified in the text expression or attribute expression.
• The '*' path element cannot be specified in the text expression or attribute expression.