Dynamic Array Formula Examples

Understanding Dynamic Array Formulas

Dynamic array formulas are a major evolution in Microsoft Excel that let a single formula output multiple values that automatically “spill” into adjacent cells. Introduced in Office 365, functions such as FILTER, SORT, SEQUENCE, UNIQUE, and the # spill operator eliminate the need for Ctrl + Shift + Enter (CSE) legacy arrays and dramatically simplify multi-value calculations.

Why Dynamic Arrays Matter to Data Engineers & Analysts

Whether you are cleaning data, prototyping business logic before pushing it into a database, or delivering ad-hoc analyses, Excel remains a universal scratch-pad for data work. Dynamic arrays make that scratch-pad behave more like a functional programming language—you write a formula once and Excel automatically sizes the output range. The result is:

• Less manual range management and fewer helper columns.
• Reduced risk of index-out-of-bounds errors when new rows arrive.
• Simpler auditing of calculation logic.
• Faster migration to SQL: the same set-based thinking used by dynamic arrays translates directly to window functions and common table expressions you might later run in a modern SQL editor like Galaxy.

Key Dynamic Array Functions

SEQUENCE()

Generates an array of sequential numbers. Syntax: =SEQUENCE(rows,[columns],[start],[step])

UNIQUE()

Returns unique values from a range or array. Syntax: =UNIQUE(array,[by_col],[exactly_once])

FILTER()

Filters a range based on Boolean criteria. Syntax: =FILTER(array,include,[if_empty])

SORT()

Sorts a range or array. Syntax: =SORT(array,[sort_index],[sort_order],[by_col])

SORTBY()

Sorts a range or array based on a parallel array. Syntax: =SORTBY(array,by_array,[sort_order])

XLOOKUP() + Spill

Although XLOOKUP is not itself an array function, it will spill if the lookup_value argument is an array.

Practical End-to-End Example

Suppose you have a transactional sales log in A2:D10000 with the columns Date, Product, Salesperson, Revenue. You want a real-time list of top-5 products by total revenue:

1. Aggregate revenue per product with SUMIFS inside UNIQUE:=LET(
   products, UNIQUE(B2:B10000),
   totals, MAP(products, LAMBDA(p, SUMIFS(D2:D10000, B2:B10000, p))),
   SORTBY(HSTACK(products, totals), totals, -1)
   )
2. Wrap the entire formula in INDEX to take only the first 5 rows:=INDEX(LET(
   products, UNIQUE(B2:B10000),
   totals, MAP(products, LAMBDA(p, SUMIFS(D2:D10000, B2:B10000, p))),
   SORTBY(HSTACK(products, totals), totals, -1)
   ), SEQUENCE(5), {1,2})

The result spills a 5×2 array showing your best-selling products and their revenue, automatically refreshing as new transactions arrive.

Best Practices

• Wrap with LET(): Use LET to store intermediate arrays and keep formulas readable.
• Plan for spill range growth: Avoid placing manual data to the right or below a dynamic array’s anchor cell.
• Use names, not offsets: Refer to structured table columns (Sales[Revenue]) so your formulas remain resilient when rows/columns move.
• Prefer MAP & LAMBDA for row-wise logic: They vectorize naturally with arrays.
• Document with comments: Dynamic arrays can become dense; keep inline comments or a README sheet.

Common Mistakes and How to Fix Them

Mistake 1: Overwriting Spill Ranges

Why it happens: Users manually enter data that collides with the dynamic array’s spill area, causing a #SPILL! error.
Fix: Keep buffer rows/columns or convert the dynamic array output into a named range referenced elsewhere.

Mistake 2: Forgetting Implicit Intersection

Why it happens: Mixing legacy formulas with dynamic arrays can unintentionally shrink an array to a single value.
Fix: Explicitly use the # operator (e.g., ) to reference the entire spill.

Mistake 3: Using Volatile Functions Excessively

Why it happens: Combining RAND(), OFFSET(), or INDIRECT() with large dynamic arrays re-calculates frequently and slows the workbook.
Fix: Replace with non-volatile alternatives like SEQUENCE, direct ranges, or helper tables.

Working Code Samples

"""Excel formulas for common scenarios"""

# 1. Generate calendar dates for the next year
a1: =SEQUENCE(365,1,TODAY(),1)

# 2. Remove duplicates from a column and sort alphabetically
a1: =SORT(UNIQUE(A2:A1000))

# 3. Two-way dynamic lookup: get latest price for each product
=MAP(UNIQUE(Products),
LAMBDA(p, XLOOKUP(1,(Products=p)*(Date=MAX(FILTER(Date,Products=p))),Price)))

# 4. Split comma-separated tags in Column A into rows below
a1: =TEXTSPLIT(A2,", ")


How Dynamic Arrays Translate to SQL (and Galaxy)

Dynamic arrays foster a set-based mindset. When you graduate from prototyping in Excel to querying production data in a SQL editor like Galaxy, many of the same constructs apply:

• UNIQUE() ≈ SELECT DISTINCT
• FILTER() ≈ WHERE clauses
• SORT()/SORTBY() ≈ ORDER BY
• SEQUENCE() ≈ GENERATE_SERIES (Postgres) or recursive CTEs
• LAMBDA functions resemble subqueries or reusable CTEs

By mastering dynamic arrays first, you’ll write clearer, more efficient SQL later—and Galaxy’s AI copilot can then auto-translate your Excel logic into SQL queries, suggest optimizations, and let you version-control endorsed queries with your team.

Frequently Asked Questions

Do dynamic array formulas work in older versions of Excel?

No. They are available only in Microsoft 365, Excel for the web, and Excel 2021 or later.

How do I stop a dynamic array from spilling?

Wrap the formula in INDEX or reference a single element with @ (implicit intersection) to constrain it to one cell.

Can I reference a dynamic array in another formula?

Yes. Append # to the anchor cell (e.g., =A2#) to capture the entire spill range.

Is there any overlap between dynamic arrays and Galaxy’s SQL editor?

While dynamic arrays live in Excel, the mental model of working with sets maps directly to SQL. Galaxy leverages that same paradigm, making it easier for spreadsheet users to transition to production-grade queries.