SQL Data Analyst Interview Questions and Answers

Experienced SQL Data Analyst with a focus on data extraction, transformation, and visualization across various industries.

• Worked on a project analyzing patient data for a healthcare provider, improving patient care through data-driven insights.

• Developed complex SQL queries to extract and manipulate large datasets, resulting in a 30% reduction in report generation time.

• Collaborated with cross-functional teams to design dashboards using Tableau, enhancing data accessibility for...read more

Query optimization involves using indexes, reducing unnecessary joins, and minimizing data retrieval.

• Use indexes on columns frequently used in WHERE clauses

• Avoid using SELECT * and only retrieve necessary columns

• Minimize the use of functions in WHERE clauses

• Reduce unnecessary joins by using INNER JOIN instead of OUTER JOIN

• Use EXISTS instead of IN for subqueries

Types of constraints in SQL include primary key, foreign key, unique, check, and not null constraints.

• Primary key constraint ensures each row in a table is uniquely identified.

• Foreign key constraint enforces referential integrity between two tables.

• Unique constraint ensures that all values in a column are unique.

• Check constraint restricts the values that can be inserted into a column.

• Not null constraint ensures a column cannot have a null value.