10+ Opkey Interview Questions and Answers

SQL Server offers various numeric data types for storing different types of numerical values.

• SQL Server provides data types like int, bigint, smallint, tinyint for storing whole numbers.

• Numeric data types like decimal and numeric are used for storing fixed-point numbers.

• Float and real data types are used for storing floating-point numbers with different precision levels.

• Money and smallmoney data types are used for storing monetary values.

Merge combines two result sets into one, while Union All combines and includes duplicates.

• Merge is used to combine two result sets into one, eliminating duplicates.

• Union All is used to combine two result sets into one, including duplicates.

• Merge requires the result sets to have the same number of columns and compatible data types.

• Union All does not require the result sets to have the same number of columns or data types.

Snowflake schema has normalized dimension tables while Star schema has denormalized dimension tables.

• Snowflake schema has a centralized fact table connected to multiple dimension tables normalized into sub-dimension tables.

• Star schema has a denormalized structure with dimension tables directly connected to the fact table.

• Snowflake schema requires more joins for querying data compared to Star schema.

• Star schema is easier to understand and query but may lead to data redundancy....read more

Snow Flake Schema has better performance than Star Flake Schema.

• Snow Flake Schema has normalized tables which reduces data redundancy and improves query performance.

• Star Flake Schema has denormalized tables which can lead to data redundancy and slower query performance.

• Snow Flake Schema is better suited for complex queries with multiple joins.

• Star Flake Schema is better suited for simple queries with fewer joins.

• Performance also depends on the specific use case and data volum...read more

Indexing in databases is a technique used to improve the speed of data retrieval by creating a data structure that allows for quick lookups.

• Indexes are created on columns in a database table to speed up the retrieval of data.

• They work similar to the index in a book, allowing the database to quickly find the rows that match a certain value.

• Examples of indexes include primary keys, unique keys, and composite indexes.

• Without indexes, the database would have to scan the entire ta...read more

Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.

• Normalization involves breaking down data into smaller, more manageable tables

• It helps in reducing data redundancy by storing data in a structured manner

• Normalization ensures data integrity by minimizing anomalies such as update, insert, and delete anomalies

• There are different normal forms like 1NF, 2NF, 3NF, and BCNF that define the level of normalization

Different row transformations in SSIS include Conditional Split, Derived Column, Lookup, and Merge.

• Conditional Split: Routes data rows to different outputs based on specified conditions.

• Derived Column: Adds new columns or modifies existing columns using expressions.

• Lookup: Retrieves data from a related table based on a specified key.

• Merge: Combines data from multiple sources into a single dataset.

Explanation of database terms: Bookmarking, Row id, Key Index, covering index.

• Bookmarking is a feature that allows users to save the location of a record in a database for future reference.

• Row id is a unique identifier assigned to each row in a table.

• Key Index is an index created on a column or set of columns that uniquely identifies each row in a table.

• Covering index is an index that contains all the columns required to satisfy a query, so the database engine does not need t...read more

Containers in SSIS are logical grouping of tasks and components that help in organizing and managing workflows.

• Containers help in organizing and managing workflows in SSIS packages

• They can be used to group related tasks together for better readability and maintenance

• Examples of containers in SSIS include Sequence Container, For Loop Container, and Foreach Loop Container

Event handlers in SSIS are workflows that are triggered by specific events during the execution of a package.

• Event handlers can be used to perform additional tasks or actions based on the success or failure of specific tasks within a package.

• Common events that can trigger event handlers include OnError, OnPreExecute, OnPostExecute, OnWarning, etc.

• Event handlers can be configured to send emails, log information, execute scripts, or perform other actions based on the event that...read more

Temp variables, tables, and CTE are used in SQL to store temporary data during query execution.

• Temp variables are used to store temporary data within a query.

• Temp tables are used to store temporary data that can be accessed by multiple queries.

• CTE (Common Table Expression) is a temporary result set that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement.

• Temp variables and tables are created using the # symbol before the variable or table name.

• CTE is create...read more

Event and error handling are crucial in SSIS to ensure smooth execution and proper handling of exceptions.

• Event handling involves capturing and responding to events that occur during package execution.

• Error handling involves identifying and handling errors that occur during package execution.

• SSIS provides various built-in event handlers and error handlers, such as OnError, OnTaskFailed, OnPostExecute, etc.

• Custom event handlers and error handlers can also be created using scri...read more

Merge combines two tables based on a specified condition, while union combines two tables with the same structure.

• Merge is used to update or insert data into a target table based on a join condition with a source table.

• Union is used to combine the results of two SELECT statements into a single result set.

• Merge requires a join condition and can perform insert, update, and delete operations.

• Union requires that both tables have the same number of columns and compatible data type...read more

Normalization is the process of organizing data in a database to reduce redundancy and dependency.

• It involves breaking down a table into smaller tables and defining relationships between them.

• Normalization helps to eliminate data inconsistencies and anomalies.

• There are different levels of normalization, with each level having specific rules to follow.

• For example, first normal form (1NF) requires that each column in a table be atomic, meaning it cannot be further divided into ...read more

Data types are classifications of data items that determine the nature of operations that can be performed on them.

• Numeric data types: int, float, double, decimal

• Character and string data types: char, varchar, text

• Date and time data types: date, time, datetime

• Boolean data type: bool

• Binary data types: binary, varbinary, image

Transformations in SSIS are used to modify data during ETL process.

• Data Conversion Transformation

• Conditional Split Transformation

• Aggregate Transformation

• Sort Transformation

• Merge Transformation

• Lookup Transformation

• Derived Column Transformation

• Multicast Transformation

• Union All Transformation

• Pivot Transformation

• Unpivot Transformation