what is – Page 146

SQL SUM() for Beginners

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.

SQL MAX() for Beginners

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.

SQL MIN() for Beginners

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.

SQL COUNT() for Beginners

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.

SQL HAVING Clause for Beginners

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.

SQL SELECT for Beginners

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.

SQL GROUP BY Clause for Beginners

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.

SQL ORDER BY Clause for Beginners

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.

How Implicit Transactions Work in SQL Server

November 11, 2025December 5, 2020 by Ian

There are four transaction modes in SQL Server. One of these is implicit mode.

In SQL Server, an implicit transaction is when a new transaction is implicitly started when the prior transaction completes, but each transaction is explicitly completed with a COMMIT or ROLLBACK statement.

This is not to be confused with autocommit mode, where the transaction is started and ended implicitly.

SQL Transactions Tutorial

December 18, 2025December 4, 2020 by Ian

In SQL, transactions are used to maintain data integrity by ensuring that a sequence of SQL statements execute completely or not at all.

Transactions manage sequences of SQL statements that must be executed as a single unit of work, so that the database never contains the results of partial operations.

When a transaction makes multiple changes to the database, either all the changes succeed when the transaction is committed, or all the changes are undone when the transaction is rolled back.