How is the usage of group_concat in pgsql?

In PostgreSQL, there is no built-in GROUP_CONCAT function, but you can achieve similar functionality using the STRING_AGG function. The STRING_AGG function is used to concatenate a column of values into a single string, with the option to specify a delimiter. The syntax is as follows:

SELECT string_agg(column_name, ', ') AS concatenated_values
FROM table_name
GROUP BY grouping_column;

In this case, column_name is the name of the column to be connected, table_name is the name of the table, and grouping_column is the name of the column for grouping. The GROUP BY clause is used to specify the columns for grouping. For example, to connect the values of a column in a table into a single string separated by commas:

SELECT string_agg(column_name, ', ') AS concatenated_values
FROM table_name
GROUP BY grouping_column;

Please note that the STRING_AGG function is only supported in PostgreSQL version 9.0 and above.