SQLServer add a default value for a column I am using MS SQL Server. I have an "action" table with an "action_type" column that I want to set a default value of "to do" for. My DDL in MS SQL Studio errors! I have read many many articles trying to work out what I am doing wrong but nothing seems to work. The DDL is as follows, the table CREATE works, and the ALTER fails.

CREATE TABLE "action"
( "action" INT IDENTITY(1,1)
, "name" VARCHAR(250) NOT NULL
, "owner" VARCHAR(50)
, "action_type" VARCHAR(50) NOT NULL
, "due_date" DATETIME
, "done_date" DATETIME
, "successful" BIT NOT NULL
, "job" INT
, "contract" INT
, "person" INT
, "description" VARCHAR(MAX)
, "deliverable" VARCHAR(MAX)
, "outcome" VARCHAR(MAX)
, "source" VARCHAR(50)
, "notes" VARCHAR(MAX)
);
ALTER TABLE "action"
ADD CONSTRAINT "df_action_0" DEFAULT "To Do" FOR "action_type";


The ALTER statement returns error 


  Msg 128, Level 15, State 1, Line 4 The name "To Do" is not permitted
  in this context. Valid expressions are constants, constant
  expressions, and (in some contexts) variables. Column names are not
  permitted.


Based on various articles I have tried replacing "To Do" with 'To Do', N'To Do', ("To Do") and others, nothing works.
It's your quotes. If you remove those, and change your literal to use single quotes, you should be fine. SQL Servers DEFAULT is SET QUOTED_IDENTIFIER ON and with this literals must be delimited by single quotation marks. So, you really only need to change this part:

DEMO

ALTER TABLE "action"
ADD CONSTRAINT "df_action_0" DEFAULT 'To Do' FOR "action_type";


Though, you will more commonly see double quotes not used in this manner, and instead your DDL would be written as:

CREATE TABLE action
( action INT IDENTITY(1,1)
, name VARCHAR(250) NOT NULL
, owner VARCHAR(50)
, action_type VARCHAR(50) NOT NULL 
, due_date DATETIME
, done_date DATETIME
, successful BIT NOT NULL
, job INT
, contract INT
, person INT
, description VARCHAR(MAX)
, deliverable VARCHAR(MAX)
, outcome VARCHAR(MAX)
, source VARCHAR(50)
, notes VARCHAR(MAX)
);

ALTER TABLE action
ADD CONSTRAINT df_action_0 DEFAULT 'To Do' FOR action_type;