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The NOT keyword is used to negate an
operation in SQL. It can be used to negate the NULL keyword when
creating a column to indicate that the column cannot have null values.
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Here is an example:
CREATE TABLE Contractors(FirstName TEXT NULL,
LastName VARCHAR NOT NULL);
This type of using NOT NULL is typically used
when creating the primary key of a table. Here is an example:
CREATE TABLE Genders(GenderID COUNTER(1,1) PRIMARY KEY NOT NULL,
Gender varchar(20));
The SQL provides the NOT operator used to
negate a statement. An example would be
NOT (Gender = "Female")
Consider a SQL statement used to get a list of
employees from the corporate department:
Private Sub cmdDataSource_Click()
RecordSource = "SELECT Employees.DateHired, " & _
" Employees.FirstName, " & _
" Employees.LastName, " & _
" Employees.Department " & _
"FROM Employees " & _
"WHERE Employees.Department = 'Corporate';"
End Sub
Imagine that, instead of getting the list of employees
who work at the corporate office, you are interested in the employees who
don't work at the corporate office. To get this list, you can negate the
"Corporate" condition that was stated earlier. This is done by preceding
the condition with NOT. This would be done as follows:
Private Sub cmdDataSource_Click()
RecordSource = "SELECT Employees.DateHired, " & _
" Employees.FirstName, " & _
" Employees.LastName, " & _
" Employees.Department " & _
"FROM Employees " & _
"WHERE NOT (Employees.Department = 'Corporate');"
txtDateHired.ControlSource = "DateHired"
txtFirstName.ControlSource = "FirstName"
txtLastName.ControlSource = "LastName"
txtDepartment.ControlSource = "Department"
End Sub