Offset
⚠️ The
Offset
function is currently unavailable for MySQL/MariaDB, MongoDB, and Druid.
The Offset
function returns the value of an expression in a different row. Offset
can only be used in the query builder’s Summarize step (you cannot use Offset
to create a custom column).
Syntax: Offset(expression, rowOffset)
The expression
is the value to get from a different row.
The rowOffset
is the number relative to the current row. For example, -1
for the previous row, or 1
for the next row.
Example: Offset(Sum([Total]), -1)
would get the value of Sum([Total])
from the previous row.
The order of the breakouts matter
Because Offset
refers to other rows, the order of the breakouts matters (the breakouts are the groups in the “Group By” section in the Summarization step). Metabase will sort by the first group, then partition by any additional breakouts. For example, if you want to see the counts of orders by product category over time, and the counts by product category for the previous period, you should first group by Created At
, then by the product category.
Data types
The Offset
function returns whatever value is in the offset row.
Data type | Returned by Offset |
---|---|
String | ✅ |
Number | ✅ |
Timestamp | ✅ |
Boolean | ✅ |
JSON | ✅ |
Example year-over-year (YoY) time series comparison using Offset
In the Sample database, you can use Offset
to compare the count of orders year over year (YoY).
First, summarize by Sum of Total. Then summarize that summation again, this time using Offset
to grab the previous row’s value.
Offset(Sum([Total]), -1)
Then group the results by Created At
by year:
Which yields:
With these offsets (the Sums in the “Previous period” column), we can then create custom columns to calculate things like the difference between yearly Sums:
[Sum of total] - [Previous period]
And the percentage change year to year:
[Difference] / [Previous period] * 100
Example rolling average using Offset
You can use a custom expression with Offset
to calculate rolling averages.
For example, let’s say you want to calculate the rolling average sum of order totals over the past three months. You could create a custom expression to calculate these rolling averages:
(Sum([Total]) + Offset(Sum([Total]), -1) + Offset(Sum([Total]), -2)) / 3
The above expression adds up this period’s total, plus the totals for the previous two periods (offset by -1
and -2
), and then divides by three to get the average across those periods.
Related functions
SQL
The Offset
function compares with SQL’s LAG
and LEAD
window functions.
For example, if you’re trying to create a line chart with two series to compare a) this month’s order counts with b) the previous month’s order counts, you’d count
the orders for this month, then use an offset
expression to count the previous month’s orders, like so:
Offset(count, -1)
Under the hood, Metabase will translate that Offset
expression into a LAG
window function, like in this query:
SELECT
"source"."CREATED_AT" AS "CREATED_AT",
COUNT(*) AS "count",
LAG(COUNT(*), 1) OVER (
ORDER BY
"source"."CREATED_AT" ASC
) AS "Order count previous period"
FROM
(
SELECT
DATE_TRUNC('month', "PUBLIC"."ORDERS"."CREATED_AT") AS "CREATED_AT"
FROM
"PUBLIC"."ORDERS"
) AS "source"
GROUP BY
"source"."CREATED_AT"
ORDER BY
"source"."CREATED_AT" ASC
Further reading
Read docs for other versions of Metabase.