Snap-on Business Solutions SQL Developer Interview Questions and Answers

Rank and Dense_Rank are window functions used to assign a rank to each row based on a specific column value.

• Rank assigns unique ranks to each row based on the column value.

• Dense_Rank assigns ranks to each row based on the column value, but skips the rank if there are ties.

• Both functions are used with the OVER() clause and ORDER BY statement.

• Example: SELECT name, salary, RANK() OVER(ORDER BY salary DESC) AS rank FROM em...read more

SET NOCOUNT ON is a T-SQL statement that stops the message indicating the number of rows affected by a Transact-SQL statement.

• SET NOCOUNT ON is used to improve the performance of stored procedures by reducing network traffic.

• It is particularly useful when executing large scripts or batch processes.

• It is also used to suppress the '(X row(s) affected)' message in SQL Server Management Studio.

• To turn it off, use SET NOCOU

COALESCE is a function that returns the first non-null value in a list of expressions.

• COALESCE is used to simplify complex SQL statements.

• It can be used with any data type.

• It takes two or more arguments and returns the first non-null value.

• If all arguments are null, it returns null.

• Example: COALESCE(column1, column2, 'N/A') will return the value of column1 if it's not null, else column2 if it's not null, else 'N/A'.

PIVOT and UNPIVOT are used to transform data from rows to columns and vice versa.

• PIVOT is used to rotate rows into columns

• UNPIVOT is used to rotate columns into rows

• PIVOT requires an aggregate function to be specified

• UNPIVOT requires the column names to be specified

• PIVOT and UNPIVOT are used in T-SQL

• Example: PIVOT (SUM(Sales) FOR Product IN ([A], [B], [C]))

• Example: UNPIVOT (Sales FOR Product IN ([A], [B], [C]))

Dense Rank and Rank are SQL functions used to assign a rank to each row in a result set based on a specified criteria.

• Dense Rank assigns unique ranks to each row, leaving no gaps in the ranking sequence.

• Rank assigns ranks to each row, leaving gaps in the ranking sequence.

• Both functions can be used with the OVER clause to partition the result set and order the ranking based on specific columns.

• Dense Rank and Rank are co...read more