GEMINI SOFTWARE SOLUTIONS Interview Questions and Answers

Performance tuning
Maintainace work on the db

Q1. What is magic table?
Ans. 
Magic table is a virtual table in SQL Server that stores the data affected by DML statements.
• Magic table is used in triggers to access the data before and after the triggering DML operation.

• In SQL Server, INSERTED and DELETED are examples of magic tables used in triggers.

• INSERTED table stores the new data for INSERT and UPDATE operations, while DELETED table stores the old data for UPDATE and DELETE operations.
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Q2. Query tuning in sql?
Ans. 
Query tuning in SQL involves optimizing SQL queries to improve performance.
• Identify slow queries using tools like query execution plans

• Optimize queries by using indexes, avoiding unnecessary joins, and rewriting complex queries

• Consider factors like data volume, indexing, and server resources

• Test query performance after tuning to ensure improvements
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Q3. Isnull() in sql?
Ans. 
ISNULL() is a SQL function used to replace NULL values with a specified value.
• ISNULL() function is used to replace NULL values with a specified default value.

• Syntax: ISNULL(expression, replacement_value)

• Example: SELECT ISNULL(column_name, 'N/A') FROM table_name;
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Q4. Project experience?
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Q5. Query writing with joins
Ans. 
Query writing with joins involves combining data from multiple tables based on a common column.
• Use JOIN keyword to combine tables based on a common column

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• Specify the columns to select from each table and the join condition in the query
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