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The Transformation Language
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- TRUNC (Dates)
- TRUNC (Numbers)
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Creating Custom Functions
Custom Function API Reference

Transformation Language Reference

10.5.7
- 10.5.6
- 10.5.1
- 10.5
- 10.4.0

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LEAD

Returns the value that is an offset number of rows after the current row in an Expression transformation. Use this function to compare values in the current row with values in a future row when you run a mapping on the Spark engine in the Hadoop environment.

A lead value appears after the current row in a set of data.

When you use LEAD in a transformation, you must configure the transformation for windowing. Windowing properties define how the data is partitioned and ordered.

Syntax

LEAD ( column_name, offset, default )

The following table describes the arguments for this command:

Argument	Required/ Optional	Description
column_name	Required	The target column or expression that the function operates on.
offset	Required	Integer data type. The number of rows after the current row to obtain a value from.
default	Optional	The default value to be returned in case the offset is outside the bounds of the partition or table. Default is NULL.

Return Value

The data type of the specified column_name
.

Default
if the return value is outside the bounds of the specified partition.

NULL if default
is omitted or set to NULL.

Examples

The following expression returns, for each employee, the date the next employee was hired:

LEAD ( HIRE_DATE, 1, NULL )

EMPLOYEE	HIRE_DATE	RETURN VALUE
Hynes	2012/12/07	2014/05/18
Williams	2014/05/18	2015/07/24
Pritchard	2015/07/24	2015/12/24
Snyder	2015/12/24	2016/11/15
Troy	2016/11/15	2017/08/10
Randolph	2017/08/10	NULL

There is no lead value available for the last row, so the function returned the default value of NULL.

The following expression returns the difference in sales quota values between the first quarter to the third quarter of two calendar years:

LEAD ( Sales_Quota, 2, 0 ) - Sales_Quota

You partition the data by year and order by quarter.

YEAR	QUARTER	SALES_QUOTA	QUOTA_DIFF
2016	1	300	7700
2016	2	7000	0
2016	3	8000	0
2017	1	5000	4000
2017	2	400	0
2017	3	9000	0

The lead values of the second and third quarter are outside the specified partition, so the function returned a value of "0."

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Table of Contents

Transformation Language Reference

Transformation Language Reference

LEAD

LEAD

Syntax

Return Value

Examples