# Understanding CSV Data

CSV means comma-separated values. Each line is a record and each position represents a field.

~~~csv
match_id,team_name,wins,losses
M001,Fictional Falcons,4,1
M002,Sample Sharks,3,2
~~~

The first row is a header. Quoted fields may contain commas, so do not process CSV with `explode(",")`; use `fgetcsv()`.

## Inspect before importing

Identify headers, data types, required fields, allowed ranges, unique identifiers, missing values and any fields that relate to other tables.

Treat every upload as untrusted input. A file being supplied with a task does not remove the need for validation.

## Check

- [ ] Headers have meaning and match expected fields.
- [ ] Every row has the expected number of columns.
- [ ] Numeric and identifier rules are documented.
- [ ] All classroom records are fictional.