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Description. The MySQL GROUP BY clause is used in a SELECT statement to collect data across multiple records and group the results by one or more columns.

## What does the group function do?

Group functions are mathematical functions to operate on sets of rows to give one result per set. The types of group functions (also called aggregate functions) are: AVG, that calculates the average of the specified columns in a set of rows, COUNT, calculating the number of rows in a set.

## How many group functions are there in MySQL?

MySQL Common Group Functions

Function | Description |
---|---|

MAX | Returns the highest value |

AVG | Returns the average value |

COUNT (*) | Returns the number of records in a table |

COUNT (column) | Returns the number of values (NULL values will not be counted) of the specified column |

## What is aggregate function MySQL?

MySQL’s aggregate function is used to perform calculations on multiple values and return the result in a single value like the average of all values, the sum of all values, and maximum & minimum value among certain groups of values.

## What is group by 1 in MySQL?

It means to group by the first column regardless of what it’s called. You can do the same with ORDER BY .

## What is the purpose of group function in SQL?

The GROUP BY statement groups rows that have the same values into summary rows, like “find the number of customers in each country”. The GROUP BY statement is often used with aggregate functions ( COUNT() , MAX() , MIN() , SUM() , AVG() ) to group the result-set by one or more columns.

## What do you understand by GROUP BY function?

The GROUP BY Statement in SQL is used to arrange identical data into groups with the help of some functions. i.e if a particular column has same values in different rows then it will arrange these rows in a group.

## Can we GROUP BY two columns in MySQL?

Yes, it is possible to use MySQL GROUP BY clause with multiple columns just as we can use MySQL DISTINCT clause. Consider the following example in which we have used DISTINCT clause in first query and GROUP BY clause in the second query, on ‘fname’ and ‘Lname’ columns of the table named ‘testing’.

## Why do we use GROUP BY and order by function in MySQL?

ORDER BY is used to sort a result by a list of columns or expressions. GROUP BY is used to create unique combinations of a list of columns that can be used to form summaries.

## What is Cube in MySQL?

Introduction to SQL CUBE

CUBE allows you to generate subtotals like the ROLLUP extension. In addition, the CUBE extension will generate subtotals for all combinations of grouping columns specified in the GROUP BY clause. … The statement creates two subtotal combinations.

## What is cross join in MySQL?

MySQL CROSS JOIN is used to combine all possibilities of the two or more tables and returns the result that contains every row from all contributing tables. The CROSS JOIN is also known as CARTESIAN JOIN, which provides the Cartesian product of all associated tables.

## Can group functions be used in where clause?

Group functions cannot be used in WHERE clause. The can appear in SELECT, HAVING and ORDER BY clause.

## What are window functions in MySQL?

A MySQL window function is a function that uses basic queries to manipulate row values. Window functions must have an OVER clause. Therefore, any function without an OVER clause is not a window function.

## What is ORDER BY 2 desc in SQL?

If you prefer, you can use the positions of the column in the ORDER BY clause. … SELECT name, credit_limit FROM customers ORDER BY 2 DESC, 1; In this example, the position of name column is 1 and credit_limit column is 2. In the ORDER BY clause, we used these column positions to instruct the Oracle to sort the rows.

## Can we use SELECT * with GROUP BY?

Cannot use an aggregate or a subquery in an expression used for the group by list of a GROUP BY clause. The original idea was to create the table in beginning of the query, so the (SELECT * FROM #TBL) could be used on the query itself, instead of defining the names on each GROUP BY.

## Can we use GROUP BY without aggregate function?

You can use the GROUP BY clause without applying an aggregate function. … In this case, the GROUP BY works like the DISTINCT clause that removes duplicate rows from the result set.