Database

• Any modifications, including UPDATE, INSERT, and DELETE statements, must reference columns from only one base table.
• The columns being modified in the view must directly reference the underlying data in the table columns. The columns cannot be derived in any other way, such as through the following:


• An aggregate function: AVG, COUNT, SUM, MIN, MAX, GROUPING, STDEV, STDEVP, VAR, and VARP.
• A computation. The column cannot be computed from an expression that uses other columns. Columns that are formed by using the set operators UNION, UNION ALL, CROSSJOIN, EXCEPT, and INTERSECT amount to a computation and are also not updatable.


• The columns being modified are not affected by GROUP BY, HAVING, or DISTINCT clauses.
• TOP is not used anywhere in the select_statement of the view together with the WITH CHECK OPTION clause.

create or replace trigger emp_dml_counter 
after update on emp 
for each row
as 
begin
  insert into emp_track values('update',1);
end;

INSERT INTO Emp_Track (DmlType, DmlCount) VALUES ('UPDATE', 0);
INSERT INTO Emp_Track (DmlType, DmlCount) VALUES ('INSERT', 0);
...

CREATE TRIGGER trg_Emp 
AFTER UPDATE ON Emp
FOR EACH ROW
BEGIN
   UPDATE Emp_Track 
   SET    DmlCount = DmlCount + 1
   WHERE  DmlType = 'UPDATE';
END;

CREATE TRIGGER trg_Emp 
AFTER UPDATE ON Emp
FOR EACH ROW
BEGIN
   UPDATE Emp_Track 
   SET    DmlCount = DmlCount + 1
   WHERE  DmlType = 'UPDATE'
   AND    DmlTime = SYSDATE;
   --
   IF SQL%ROWCOUNT = 0 THEN
      INSERT INTO Emp_Track (DmlType, DmlCount, DmlTime)
      VALUES ('UPDATE', 1, SYSDATE);
   END IF;
END;

JenovaProject wrote:

Is there a way to build a table so that no team can play two games on the same date

ALTER TABLE XYZ ADD CONSTRAINT UK_SingleGame UNIQUE (date, home_id);