Synechron SQL Server Developer Interview Questions and Answers

Types of joins in SQL are Inner Join, Left Join, Right Join, and Full Join.

• Inner Join: Returns rows when there is a match in both tables.

• Left Join: Returns all rows from the left table and the matched rows from the right table.

• Right Join: Returns all rows from the right table and the matched rows from the left table.

• Full Join: Returns rows when there is a match in one of the tables.

GROUP BY is used to group rows that have the same values into summary rows, while HAVING is used to filter groups based on a specified condition.

• GROUP BY is used with aggregate functions to group the result set by one or more columns.

• HAVING is used to filter groups based on a specified condition after the GROUP BY clause.

• GROUP BY is used before the HAVING clause in a query.

• Example: SELECT department, COUNT(*) FROM empl...read more

DML commands are Data Manipulation Language commands used to manage data in a database.

• DML commands include INSERT, UPDATE, DELETE, and SELECT.

• INSERT is used to add new rows of data into a table.

• UPDATE is used to modify existing data in a table.

• DELETE is used to remove rows of data from a table.

• SELECT is used to retrieve data from a database.

Primary key uniquely identifies each record in a table, while Unique key allows only one instance of a value in a column.

• Primary key does not allow NULL values, while Unique key allows one NULL value.

• Primary key automatically creates a clustered index, while Unique key creates a non-clustered index by default.

• Primary key can be referenced by foreign keys, while Unique key cannot be referenced by foreign keys.

Indexes are data structures that improve the speed of data retrieval operations in a database.

• Indexes are used to quickly locate data without having to search every row in a database table.

• Types of indexes include clustered, non-clustered, unique, and composite indexes.

• Clustered indexes determine the physical order of data in a table, while non-clustered indexes store a separate copy of the indexed columns.

• Unique index...read more

Execution plan is a roadmap that SQL Server uses to execute a query, showing the steps taken to retrieve data.

• Execution plan is generated by the query optimizer to determine the most efficient way to execute a query.

• It shows the order in which tables are accessed, joins are performed, and filters are applied.

• Execution plan can be viewed using tools like SQL Server Management Studio or by using the EXPLAIN statement in ...read more

SQL query to retrieve the maximum salary for each department

• Use the MAX() function to find the maximum salary

• Group the results by department using the GROUP BY clause

• Join the employee table with the department table to get the department information

Generate unique match pairs from a single-column team table using SQL.

• Use a self-join on the TEAM table to create pairs.

• Ensure to filter out duplicate matches by using a condition like t1.teamname < t2.teamname.

• Example SQL query: SELECT t1.teamname AS Team1, t2.teamname AS Team2 FROM TEAM t1, TEAM t2 WHERE t1.teamname < t2.teamname;

Different types of SQL joins with given data sets a and b.

• Inner join: Returns rows where there is a match in both tables (1,1)

• Left join: Returns all rows from the left table and the matched rows from the right table (1,1,1,2,2)

• Right join: Returns all rows from the right table and the matched rows from the left table (1,1,2,4)

• Cross join: Returns the Cartesian product of the two tables (1,1,1,1,1,2,1,4,1,1,2,1,2,2,1,4,2,...read more

row_number, rank, dense_rank are window functions in SQL used to assign a unique number to each row based on specified criteria.

• row_number() assigns a unique sequential integer starting from 1 to each row in the result set

• rank() assigns a unique rank to each row based on the specified ordering criteria, with gaps in ranking for ties

• dense_rank() assigns a unique rank to each row based on the specified ordering criteria,...read more

A trigger is a special type of stored procedure that automatically executes when certain events occur in a database.

• Triggers can be used to enforce business rules, maintain referential integrity, and automate repetitive tasks.

• Examples of trigger events include INSERT, UPDATE, and DELETE operations on a table.

• Triggers can be defined to execute before or after the triggering event.

Functions return a value, while stored procedures do not. Functions can be used in SELECT statements, stored procedures cannot.

• Functions return a single value, while stored procedures can return multiple values or none at all.

• Functions can be used in SELECT statements to return a value, while stored procedures cannot be used in this way.

• Functions can be called from within stored procedures, but stored procedures cannot...read more