How can I combine three records into one in postgresql and include new columns with the combined values?

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You can use the GROUP BY clause along with aggregate functions like SUM, AVG, etc. to combine multiple records into one. For example, if you have three records with columns col1, col2, and col3, you can group them by a common column and sum their values using the following query:

SELECT common_col, SUM(col1) AS total_col1, SUM(col2) AS total_col2, SUM(col3) AS total_col3
FROM your_table
GROUP BY common_col

This query will create a new column for each original column with the combined values, using the SUM function. You can also use other aggregate functions depending on your requirements.