The data you already have is worth more than you might think. Customers, sites, equipment and years of past jobs tell you how your business actually works. Nobody wants to retype it, and nobody should have to.
Export what you've got
Almost any spreadsheet can be saved as a CSV file. In most programs it's File, then Save As or Download, then CSV. Make one file per list: one for customers, one for sites, one for jobs.
Tidy the headings
The first row should be clear column names like Customer Name, Address, Email and Phone. Short, plain headings make it much easier to match columns during the import.
Fix the big problems only
Before importing, sort out the things that genuinely cause trouble:
- duplicate customers spelt slightly differently
- dates written in different formats in the same column
- several pieces of information squeezed into one cell
Don't spend a week polishing. You can tidy up inside the new system.
Import in the right order
If your lists refer to each other, import the ones others depend on first. Customers before sites, sites before jobs. Then when the jobs arrive, the customers and sites they mention already exist.
Decide about duplicates
If you import the same list twice, or add to data that's already there, choose what happens to matching rows: skip them, update them or create new ones. Matching on something like a reference number or email address keeps it tidy.
Big files
Thousands of rows shouldn't be a problem, but they should go in batches, so one bad row doesn't stop everything and you can see what failed and try again.
OmniSchema imports CSV files straight into any list. Large files go in batches you can pause, resume and retry. You choose whether to skip or update rows that match on a column you pick, and names in an Assignee column are matched to real people in your team automatically.