Join Choice and Impact | Dataford Interview Questions

Explain the difference between a left join and an inner join, and provide a real-world scenario where using the wrong one would corrupt your analysis.

For the SQL portion, calculate filing counts while preserving accounts that have no filings.

Output

One row per account, with account_name and filing_count.
Include every account, including accounts with zero filings.
Order by account_id ascending.

Schema

accounts

Column	Type	Description
account_idPK	INT	Unique account identifier
account_name	VARCHAR(100)	Account display name
account_type	VARCHAR(30)	Account classification

tax_filings

Column	Type	Description
filing_idPK	INT	Unique filing identifier
account_id	INT	Account associated with the filing
filing_period	VARCHAR(20)	Tax filing period
filing_status	VARCHAR(30)	Current filing status

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Problem