MS SQL Server: Setting Default Values for Fields Using MS SQL Server Defaults

Introduction

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. GETDATE() for a timestamp field, by setting column default values in the table definition.

Note

The MS SQL Server 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 GETDATE().

Console

Open the console and head to Data -> [article] -> Modify.

Click the Edit button next to the created_at field and add GETDATE() as a default value.

API

You can add a default value by using the mssql_run_sql schema API:

POST /v2/query HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin

{
  "type": "mssql_run_sql",
  "args": {
    "source": "<db_name>",
    "sql": "ALTER TABLE article ADD CONSTRAINT DF_article DEFAULT GETDATE() FOR created_at;"
  }
}

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.

Run the following SQL command to create a new sequence.

CREATE SEQUENCE roll_number_seq AS INT START WITH 0 INCREMENT BY 1;

Now set the default value of the roll_number field as DEFAULT (NEXT VALUE FOR 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 MS SQL Server.

GraphiQL

Query Variables

Request Headers

Also see

• MS SQL Server: Setting values for fields using role-based column presets