How Can I Return Multiple Fields from Different PostgreSQL Tables as a Single Record Using PL/pgSQL?

Returning Multiple Fields as a Record in PostgreSQL with PL/pgSQL

When working with PL/pgSQL, you may encounter the need to return a record that combines fields from multiple tables. This can be achieved by leveraging Postgres's RECORD data type.

Using RECORD for Multi-table Field Retrieval

To return fields from different tables as fields in a single record, define the desired fields within a RECORD type as follows:

CREATE OR REPLACE FUNCTION get_object_fields(name text)
RETURNS RECORD AS $$
BEGIN
  -- Retrieve required fields from various tables based on input name

  -- Return fields as a RECORD
  RETURN RECORD(f1, f2, f3, f4, f5, f6, f7, f8);
END
$$ LANGUAGE PL/pgSQL;

Handling Multiple Result Rows

For complex scenarios where rows with multiple field values need to be "flattened" into a single record, a more involved approach is necessary. Consider the following code:

CREATE OR REPLACE FUNCTION get_two_users_from_school(schoolid int)
RETURNS my_type AS $$
DECLARE
  result my_type;
  temp_result user;
BEGIN
  -- Fetch two rows for illustration
  SELECT id, name INTO temp_result FROM user WHERE school_id = schoolid LIMIT 2;

  -- Assign values to the RECORD fields using pseudocode (adjust indices for actual row counts)
  result.user1_id := temp_result[0].id;
  result.user1_name := temp_result[0].name;
  result.user2_id := temp_result[1].id;
  result.user2_name := temp_result[1].name;

  RETURN result;
END
$$ LANGUAGE PL/pgSQL;

Benefits of the Record Type

The RECORD type provides several advantages:

• It allows for the creation of complex data structures with a consistent format.
• It can accommodate a varying number of fields, allowing for flexibility in results.
• It simplifies data retrieval, as it returns multiple fields as a single object.

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