Repeated Vacancy Advertisements

SQL practice question · Easy · Aggregation · LinkedIn

vacancy_ads has one row per job listing (company_id, title, job_id). A company has a duplicate listing when it posted two or more listings with exactly the same title. Count how many distinct companies have at least one duplicate listing (a company with several duplicated titles is counted once). Output a single column: duplicate_companies.

Table: vacancy_ads

Schema of vacancy_ads
ColumnType
company_idINTEGER
titleTEXT
job_idINTEGER
Sample rows of vacancy_ads
company_idtitlejob_id
1Data Analyst10
1Data Analyst11
1Engineer12
2Data Analyst13
2Data Analyst14
3Designer15
Expected output on the sample data
duplicate_companies
2

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