Page 87 - SQL

RESULTS

city_name avg_population

New York City 8,250,754

Note: The AVG() function will convert values to numeric types. This is especially
important to keep in mind when working with dates.

List Concatenation

Partial credit to this SO answer.

List Concatenation aggregates a column or expression by combining the values into a single string
for each group. A string to delimit each value (either blank or a comma when omitted) and the
order of the values in the result can be specified. While it is not part of the SQL standard, every
major relational database vendor supports it in their own way.

MySQL

SELECT ColumnA
, GROUP_CONCAT(ColumnB ORDER BY ColumnB SEPARATOR ',') AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;

Oracle & DB2

SELECT ColumnA
, LISTAGG(ColumnB, ',') WITHIN GROUP (ORDER BY ColumnB) AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;

PostgreSQL

SELECT ColumnA
, STRING_AGG(ColumnB, ',' ORDER BY ColumnB) AS ColumnBs
FROM TableName
GROUP BY ColumnA
ORDER BY ColumnA;

SQL Server

https://riptutorial.com/ 69