SQL Practice
SQL 75
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Skill Topics
Basics & Filtering Aggregation & Grouping Joins (All Types) Subqueries & Correlated CTEs & Adv. Subqueries Window Functions Advanced & Tricky Schema Design & Opt.
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75. Scalar Subquery Select

Hard Subqueries & CTEs
Query Rules
  • The query columns and order must match the expected result schema.
  • NULL values should be handled appropriately where applicable.
  • The grader compares output values and sorting order to evaluate.

Schema Browser

Click a table's header to toggle expand/collapse.
patients
10 cols
doctors
4 cols
admissions
7 cols
province_names
2 cols

Reference Solution

Expected SQL 
SELECT first_name, (SELECT COUNT(*) FROM admissions a WHERE a.patient_id = p.patient_id) AS admission_count FROM patients p;
SQL Editor
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Console Output

Console Terminal

Write your query and click "Run Query" (Ctrl + Enter) to see results and testcase validation.

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