Setting default values for fields using Postgres defaults¶
Table of contents
You can set values of certain fields automatically when not explicitly passed to a fixed value, e.g. true for a boolean field, or output of a simple SQL function, e.g. now() for a timestamp field, by setting column default values in the table definition.
Note
The Postgres default value is ignored when a value is explicitly set to the field.
Example: Say we have a field created_at in a table article which we want to be set to the current
timestamp whenever a new row is added to the table:
Step 1: Modify the table¶
Edit the created_at field and set its default value as the SQL function now().
Open the console and head to Data -> article -> Modify:
To set an auto-incrementing default value
To set a default value as an auto-incrementing integer you first need to set up a sequence which will be the
source of our default value.
Let’s say we have a field called roll_number which we would like to be set by default as an auto-incremented
integer.
Head to Data -> SQL and run the following SQL command to create a new sequence.
CREATE SEQUENCE roll_number_seq;
Now set the default value of the roll_number field as nextval('roll_number_seq').
Step 2: Run an insert mutation¶
Now if you do not pass the created_at field value while running an insert mutation on the article table, its
value will be set automatically by Postgres.
mutation { insert_article( objects: [ { title: "GraphQL manual", author_id: 11 } ]) { returning { id title created_at } }}xxxxxxxxxx{ "data": { "insert_article": { "returning": [ { "id": 12, "title": "GraphQL manual", "created_at": "2020-04-23T11:42:30.499315+00:00" } ] } }}