create query – Page 13

SQL UNION Clause for Beginners

October 22, 2023December 8, 2020 by Ian

In SQL, the UNION clause concatenates the results of two queries into a single result set.

You can use the UNION clause with or without the ALL argument:

Some RDBMSs also accept UNION DISTINCT, which is the equivalent to UNION. That is, it excludes duplicates.

Below are some basic examples to demonstrate how it works.

July 23, 2023December 8, 2020 by Ian

In SQL, the AVG() function is an aggregate function that returns the average of all values in a given expression.

It can also be used to return the average of all distinct (unique) values in an expression.

The expression must be numeric (it cannot be character string, bit string, or datetime).

Below are some basic examples to demonstrate how it works.

July 23, 2023December 8, 2020 by Ian

In SQL, the SUM() function is an aggregate function that returns the sum of all values in a given expression.

It can also be used to return the sum of all distinct (unique) values in an expression.

The expression must be numeric (it cannot be character string, bit string, or datetime).

Below are some basic examples to demonstrate how it works.

July 23, 2023December 7, 2020 by Ian

In SQL, the MAX() function is an aggregate function that returns the maximum value in a given expression.

Below are some basic examples to demonstrate how it works.

July 23, 2023December 7, 2020 by Ian

In SQL, the MIN() function is an aggregate function that returns the minimum value in a given expression.

Below are some basic examples to demonstrate how it works.

July 23, 2023December 7, 2020 by Ian

In SQL, the COUNT() function is an aggregate function that returns the number of items found in a group.

You can use COUNT() in multiple parts of a query. For example, you can use it in the SELECT list, or the HAVING clause when filtering groups.

December 7, 2020December 6, 2020 by Ian

In SQL, the HAVING clause can be used to specify a search condition for a group or an aggregate.

The HAVING clause is typically used with the GROUP BY clause. In cases where it’s not, there is an implicit single, aggregated group.

September 17, 2024December 6, 2020 by Ian

The SELECT statement is almost without doubt, the most commonly used statement in SQL.

The SELECT statement is used for retrieving data from the database. You can specify which rows you want returned, and which columns.

December 7, 2020December 5, 2020 by Ian

In SQL, the GROUP BY clause can be used to divide the results of a query into groups of rows.

This is usually done in order to perform one or more aggregations on each group.

December 5, 2020 by Ian

The ORDER BY clause is commonly used in SQL to sort the results of a query.

It allows you to specify the order in which the results are returned.

You can specify whether the results are sorted in ascending order or descending order. You can also specify multiple columns for sorting.