SSMS Invalid Column name

Sometimes the Cache of SSMS gets “corrupted” or fails to update, this can lead to Red squiggles under column namnes, table names, basiacally anything (Also SSMS will claim the name does not exist with for instance the error message invalid column namn).
When this error lies in SSMS, then refreshing the cache is the solution, and this is done with “Ctrl-Shitf-R

SQLServer Adding a column to a table

Adding a column to existing table is not that hard. One thing to keep in mind, if the column is not nullable then a default value is mandatory.

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} 
DEFAULT {DEFAULT_VALUE}