Replace your check constraint with a referential constraint.Add a referential constraint to some table that has a row for male and a row for female. You can at a later date add more genders to handle cases like earth worms.It is simplest to use the single characters 'm' and 'f'. Some people make a distinction between gender and sex.I will supplement that with this post about representing sex (gender) in people records. The word 'sex' is not too long, its characters are all Latin, there is no need to "delimit", using lower case is okay, making it plural ('sexes') would be a mistake, and it's not a reserved word. In that case, 'sex' is better if only a physical characteristic matters, but 'gender' is better if you're also taking into account the behaviour, self-identification, and washroom preference. If there are application programs that use the database, what checkboxes are they likely to display?Your suggestions for corrections would be appreciated. is.na(a)]  2 3 3 1 3 4 5 3 4 3 2 1 2 2 2 2 1 In the case of a data frame (which a grouped Data object contains), you can use complete.cases() to access the rows that do not have missing values.
1 idnum Char 4 24 3 jobcode Char 3 29 4 salary Num 8 0 2 sex Char 1 28-----Alphabetic List of Variables and Attributes----- # Variable Type Len Pos Format Informat 5 birth Num 8 8 DATE9. 4 DEPT Char 6 40 1 EMPID Num 8 0 9 FRSTNAME Char 15 65 6 GENDER Char 1 46 2 HIREDATE Num 8 8 DATE9.It's worth a look even if your German is weak, because most of the charts include English translations.