i have a table called 'tblDive' with columns: 

```
create table tblDive (
DiveNumber int
InstructorNumber int
ClubNumber int
InstructorSigniture date
)

```

and another table:

```
create table tblWorksAt (
InstructorNumber int
ClubNumber int
StartWorkingDate date
EndWorkingDate date
)

```

the table 'tblWorksAt' has this record:

```
InstructorNumber | ClubNumber | StartWorkingDate | EndWorkingDate
       1               2            1.1.2000          1.1.2005

```

i want to create a trigger that checks when inserting a new dive, if the instructor really worked at this club in the same time of signing on the dive.
so for example if i insert a new dive:

```
insert into tblDive (DiveNumber InstructorNumber ClubNumber InstructorSigniture) 
values 111, 1, 2, 1.1.2009

```

i won't be able to insert this record because instructor number 1 stopped working at club number 2 in 1.1.2005