Impetus Technologies Module Lead Interview Questions, Process, and Tips

SCD Types refer to Slowly Changing Dimensions Types used in data warehousing.

• SCD Type 1: Overwrite the old data with new data

• SCD Type 2: Create a new record for the new data and keep the old record

• SCD Type 3: Add new columns to the existing record to store new data

• SCD Type 4: Create a separate table to store historical data

• SCD Type 6: Combination of Type 1 and Type 2

Join types in SQL are used to combine data from two or more tables based on a related column.

• Inner join returns only the matching rows from both tables

• Left join returns all rows from the left table and matching rows from the right table

• Right join returns all rows from the right table and matching rows from the left table

• Full outer join returns all rows from both tables, with NULL values in the columns where there is no

Optimization techniques in SQL query

• Use indexes to speed up query execution

• Avoid using SELECT * and only select necessary columns

• Use subqueries instead of joins for small tables

• Use UNION ALL instead of UNION if possible

• Avoid using functions in WHERE clause

• Use EXPLAIN to analyze query performance