In this SQL tutorial for beginners, you will create your own database, insert data into that database, and then run queries against that database.
This SQL tutorial will get you running SQL queries in no time!
Continue readingAuthor: Ian
How to Rename a Column in SQL
This article provides a quick example of renaming a table in SQL.
Most of the major RDBMSs allow you to rename a column with the ALTER TABLE statement. SQL Server is an exception.
SQL ALTER TABLE for Beginners
In SQL, the ALTER TABLE statement modifies the definition of an existing table.
You can use ALTER TABLE to alter, add, or drop columns and constraints.
Depending on your DBMS, the ALTER TABLE statement can also be used to reassign and rebuild partitions, or disable and enable constraints and triggers.
SQL UNION Clause for Beginners
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:
UNION ALL– Includes duplicates.UNION– Excludes duplicates.
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.
Continue readingSQL AVG() for Beginners
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.
Continue readingSQL SUM() for Beginners
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.
Continue readingSQL MAX() for Beginners
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.
Continue readingSQL MIN() for Beginners
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.
Continue readingSQL COUNT() for Beginners
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
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.