We can use the PostgreSQL array_agg in multiple columns to aggregate it into arrays. As part of our PostgreSQL Support, Bobcares provides answers to all of your questions.

PostgreSQL array_agg in Multiple Columns

PostgreSQL’s array_agg function is handy for aggregating data into arrays, but it’s designed to handle one column at a time. However, we can still aggregate multiple columns into a single array using a couple of methods.

1. Row Concatenation:

This method involves creating a new row for each group by concatenating the desired columns. Then, we can use array_agg to aggregate these new rows into an array of “combined rows”.

2. Custom Type and Array Constructor:

If we often need to combine multiple columns into arrays, we can consider creating a custom data type to represent this structure.

Let’s see the details of this method:

Define a Custom Type: Create a composite data type containing the desired columns.

Convert Rows to Custom Type: Use a subquery or a CASE statement to convert each row into the custom type format.

Aggregate using array_agg: Finally, use array_agg to aggregate the custom type elements into an array.

An Example

This example shows us how to use array_agg on multiple columns in PostgreSQL:

This query concatenates values from the columns e_id and e_name into a single string separated by a dash (-) and aggregates them into an array using array_agg.

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Conclusion

To conclude, the article offers a brief insight from our Experts on using PostgreSQL array_agg in multiple columns to aggregate it into arrays.