How to fix Column in table is invalid for creating a default constraint

Question: I was attempting to create a constraint and getting this error 

Msg 1752, Level 16, State 0, Line 5
Column 'col1' in table 'MyTable' is invalid for creating a default constraint.
Msg 1750, Level 16, State 0, Line 5
Could not create constraint or index. See previous errors.

1. A computed column.
2. A column that doesn't exist.

How can I fix this issue?

Answer:    As part of this error message - there are two reasons presented 

       1.A computed column.

       2. A column that doesn't exist.

Based on the table DDL - there are two ADD CONSTRAINTS below which will fail - the first is an example of trying to add a CONSTRAINT to a computed column and the second is to add a CONSTRAINT to a column which doesn't exist!

CREATE TABLE dbo.MyConstraintTest
  (
     ID INT IDENTITY(1, 1) NOT NULL,
     Computed AS 'testcompute'
  ) 

--this will fail as constraints on computed columns are not allowed
  ALTER TABLE dbo.MyConstraintTest
  ADD CONSTRAINT C0 DEFAULT '1' FOR Computed

--this will fail as the column does not exist 
ALTER TABLE [dbo].[MyConstraintTest]
  ADD CONSTRAINT [randomDateColumn] DEFAULT (GETDATE()) FOR  randomDateColumn

Check the columns you're attempting to add the CONSTRAINT. 

Read more on CONSTRAINTS

How to list constraints of a table (SQL Server DBA)

Script to DROP CONSTRAINT and ADD CONSTRAINT for all CHECK CONSTRAINTS