In MariaDB, the COUNT() aggregate function returns a count of the number of non-NULL values of an expression in the rows retrieved by a SELECT statement.
Tag: aggregation
AVG() Function in MariaDB
In MariaDB, the AVG() function returns the average value of the given expression.
The DISTINCT option can be used to return the average of the distinct values (i.e. remove duplicates before calculating the average).
NULL values are ignored.
SUM() Function in MariaDB
In MariaDB, the SUM() aggregate function returns the sum of a given expression.
It can also be used to return the sum of all distinct (unique) values in an expression.
Continue readingMIN() Function in MariaDB
In MariaDB, MIN() is an aggregate function that returns the minimum value in a given expression.
MAX() Function in MariaDB
In MariaDB, MAX() is an aggregate function that returns the maximum value in a given expression.
PostgreSQL GROUP_CONCAT() Equivalent
Some RDBMSs like MySQL and MariaDB have a GROUP_CONCAT() function that allows you to return a query column as a delimited list (for example, a comma separated list).
PostgreSQL has a similar function called STRING_AGG(). This function works in pretty much the same way that GROUP_CONCAT() works in MySQL and MariaDB.
Oracle GROUP_CONCAT() Equivalent
Some RDBMSs have a GROUP_CONCAT() function that allows you to return a query column as a delimited list (for example, a comma separated list). MySQL and MariaDB are two that have such a function.
PostgreSQL and SQL Server have similar functions called STRING_AGG().
Oracle, on the other hand, has the LISTAGG() function that does pretty much the same thing (and perhaps more).
So you could say that LISTAGG() is Oracle’s GROUP_CONCAT() equivalent.
How to Return Query Results as a Comma Separated List in PostgreSQL
In Postgres, we can use the STRING_AGG() function to transform our query results into a comma separated list.
Instead of each value being output in a separate row (as with any regular query), the values are output to a single row, separated by a comma (or some other delimiter of our choosing).
Continue readingGROUP_CONCAT() Function in MySQL
MySQL has a GROUP_CONCAT() function that enables us to return columns from a query as a delimited list.
It returns a string result with the concatenated non-NULL values from a group.
LISTAGG() Function in Oracle
In Oracle, the LISTAGG() function enables us to combine data from multiple rows in to a single row.
We have the option of specifying a separator (such as a comma). We can also order the results produced by the LISTAGG() function, and more.