adf-expression

ADF Expression Generator

Generate Azure Data Factory expressions for common scenarios.

Task

Create valid ADF expressions based on the described requirement.

Arguments

• $ARGUMENTS: Description of what the expression should do
  • Example: yesterday's date in yyyy-MM-dd format
  • Example: partition path like year=2025/month=01/day=15
  • Example: first day of current month
  • Example: extract filename from full path
  • Example: check if weekday
  • Example: conditional SQL query based on parameter

Expression Syntax Rules

Basic Syntax

• Expressions start with @ prefix
• Use @{expression} for string interpolation
• Nested functions: @function1(function2(value))

Expression vs String Interpolation

// Full expression (returns typed value)
"value": "@utcnow()"

// String interpolation (returns string)
"value": "Date is @{utcnow()}"

// Explicit expression type
{
  "value": "@concat('prefix_', pipeline().parameters.Name)",
  "type": "Expression"
}

Common Expression Patterns

Date/Time

Yesterday's Date:

@formatDateTime(adddays(utcnow(), -1), 'yyyy-MM-dd')

First Day of Month:

@formatDateTime(startOfMonth(utcnow()), 'yyyy-MM-dd')

Last Day of Previous Month:

@formatDateTime(adddays(startOfMonth(utcnow()), -1), 'yyyy-MM-dd')

Date Partition Path (year/month/day):

@concat(
  formatDateTime(utcnow(), 'yyyy'), '/',
  formatDateTime(utcnow(), 'MM'), '/',
  formatDateTime(utcnow(), 'dd')
)

Hive Partition Path:

@concat(
  'year=', formatDateTime(pipeline().parameters.ProcessDate, 'yyyy'),
  '/month=', formatDateTime(pipeline().parameters.ProcessDate, 'MM'),
  '/day=', formatDateTime(pipeline().parameters.ProcessDate, 'dd')
)

Is Weekday Check:

@and(greater(dayOfWeek(utcnow()), 0), less(dayOfWeek(utcnow()), 6))

N Days Ago:

@formatDateTime(adddays(utcnow(), -7), 'yyyy-MM-dd')

String Operations

Extract Filename from Path:

@substring(
  variables('FilePath'),
  add(lastIndexOf(variables('FilePath'), '/'), 1),
  sub(length(variables('FilePath')), add(lastIndexOf(variables('FilePath'), '/'), 1))
)