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NOT NULL Constraint

In Firebird, columns are nullable by default.The NOT NULL constraint specifies that the column cannot take NULL in place of a value.

A NOT NULL constraint can only be defined as a column constraint, not as a table constraint.

SQL SECURITY Clause

The SQL SECURITY clause specifies the security context for executing functions referenced in computed columns, and check constraints, and the default context used for triggers fired for this table.When SQL Security is not specified, the default value of the database is applied at runtime.

See also SQL Security in chapter Security.