Re: What is the proper default value for VARCHAR?

[Rick James]

I think this is the set of actions:

** What happens if you do not provide a value for the column:
Table definition     || value put into table
NULL                 || NULL
NOT NULL             || '' (or 0 for numeric); plus Warning "doesn't have default"
DEFAULT 'x' NULL     || 'x'
DEFAULT 'x' NOT NULL || 'x'

** What happens if you provide NULL:
NULL                 || NULL
NOT NULL             || Error: "cannot be null"
DEFAULT 'x' NULL     || NULL
DEFAULT 'x' NOT NULL || Error: "cannot be null"

** What happens if you provide 'zz':
NULL                 || 'zz'
NOT NULL             || 'zz'
DEFAULT 'x' NULL     || 'zz'
DEFAULT 'x' NOT NULL || 'zz'

Also, AUTO_INCREMENT and certain TIMESTAMP and DATETIME columns have special actions when given no value, or NULL.