DataMosaicThe DataMosaic blog
Why the numbers don’t match, and what to do about it.
Guides, templates and fixes for retail IT teams who look after more than one system. A new one every day.
Editor’s pick · 6 min
POS vs ERP sales: why they don’t match, and how to check every night
Six reasons a store’s till total and the ERP drift apart, how to tell which one you are looking at, and the query that checks every store before nine.
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RSS feedInventory accuracy formula: three measures on one count
One store, ten lines, one count. Worked out three ways, it scores 50%, 94.8% and 90.9%, and the honest answer depends on the question you are asking.
Square inventory not updating: 7 causes and a per-store test
The sale went through and the count stayed where it was. Seven causes, what each one leaves behind, and one export that shows them across every store.
Shopify POS not updating inventory: 6 store-side causes and a test
The sale went through at the till and the count didn't follow. Six causes that live in the store, and the pattern each one leaves when you line up every location.
Compare data between two databases: SQL Server to Oracle in 3 steps
Tills on SQL Server, the ERP on Oracle, one invented day of sales: totals first, then a row hash both engines agree on, and the five type traps that make equal rows look different.
Compare two columns with VLOOKUP, XLOOKUP or Power Query
Three ways to match two lists on a key, run on one invented price file, and the two traps that make a lookup say a row is missing when it isn't.
Compare two tables in SQL for differences: three queries that work
EXCEPT both ways, a full outer join on the key, and a hash per row, run on one invented day of sales, with the NULL traps that make each one lie.
Best data reconciliation tools for retail IT in 2026, compared
Finance platforms, table compare tools, pipeline diffs, Power Query and DataMosaic: what each one answers, and which job in a store chain needs which.
Compare two CSV files for differences: in Excel, Python and PowerShell
When the rows come in a different order, match them on a key first. Three ways to do it, and the four things that make identical files look different.
How to compare two Excel files and highlight differences
Three ways, from one formula to a lookup on a key, and how to tell which one your files need.
Data reconciliation: techniques, and a worked retail example
Counts, totals, keys, fields, hashes and grain: what each technique catches and misses, worked through on one chain’s Monday morning.
Free inventory reconciliation template (Excel)
Counted stock against system stock, store by store, with the variance, its value and the record accuracy worked out for you. No sign-up.
Shopify inventory not updating: 9 causes, and how to catch the next one
Locations, sync intervals, untracked items, and the one nobody checks: an error the connector logged and moved past.