Deal with NULL in Postgres

#Data Warehouse #Postgres #PGSQL

Please deal with null carefully.

SUM up some values with NULL in it, we get a value.

WITH base AS (
    SELECT
        1 AS num
    UNION ALL
    SELECT
        2 AS num
    UNION ALL
    SELECT
        NULL AS num
)
SELECT
    SUM(num)
FROM
    base

gives us

3

However, if one would add some values up, we get a NULL when one of them is NULL.

SELECT
NULL + 10 AS null_plus_num

gives us a

NULL

Published: by ;

Authors: Lei Ma

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  • til/data/postgres.deal-with-null.md