In PostgreSQL, we can use the STRING_AGG() function to return columns from a query as a delimited list.
Tag: aggregate functions
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.
SQLite Aggregate Functions
This page contains a list of aggregate functions that are available in SQLite by default.
Continue readingHow Group_Concat() Works in SQLite
SQLite has a group_concat() function that allows you to concatenate multiple results returned for a column into one.
This is sometimes referred to as “string aggregation”.
For example, when querying a database, instead of having each column’s value output in a new row, you can use group_concat() to have them output as a comma separated list.
Tweak your Avg() Results in SQLite with the DISTINCT Keyword
If you know about the avg() function in SQLite, you’re probably aware that it returns the average of all non-NULL X within a group.
But did you know you can add the DISTINCT keyword to this function?
If you add the DISTINCT keyword, avg() will calculate its results based on distinct values only. This is essentially the same as removing duplicate values and then calculating the average on the remaining values.