如何使用 Postgres SQL 将行转换为列？

Question

I have the data in the following structure

Desired Output

Answer 1

Postgres (starting in 9.4) supports the filter syntax for conditional aggregation. So I would recommend:

SELECT customer_id,
       MAX(value) FILTER (WHERE name = 'age') as age,
       MAX(value) FILTER (WHERE name = 'marketing_consent') as marketing_consent,
       MAX(value) FILTER (WHERE name = 'gender') as gender
FROM t
GROUP BY customer_id

Answer 2

SELECT customer_id,
    MAX(CASE WHEN name='age' THEN value ELSE NULL END) AS age,
    MAX(CASE WHEN name='marketing_consent' THEN value ELSE NULL END) AS marketing_consent,
    MAX(CASE WHEN name='gender' THEN value ELSE NULL END) AS gender
FROM table
GROUP BY customer_id;

You just group by customer_id and pick out each value in its own column. You need an aggregate function on the various values columns for syntactical reasons, which is why each column has a Max function.

Not e that it would of course be better to store the data in a normalized fashion. Also, with newer versions of postgres, you can use filter instead of case, which I find a bit more readable.