hunchback
asked on
concatenated keys in Sybase SQLANYwhere
CREATE TABLE emp_skill(
emp_id INTEGER NOT NULL,
skill_id INTEGER NOT NULL,
"skill level" INTEGER NOT NULL,
PRIMARY KEY( emp_id, skill_id ),
FOREIGN KEY REFERENCES employee,
FOREIGN KEY REFERENCES skill
)
--------------------------
how does a "concatenated" key work in the above example? if you want to link to it from another table -- u have gotta have a 'concatenated' key there too? u obviously can't join to the above table if u got only emp-id..
if i use SQLCentral i can't get to see/define if the combination of both is unique or not.
if this concatenated key is a foreign key somewhere else - how is it implemented?
emp_id INTEGER NOT NULL,
skill_id INTEGER NOT NULL,
"skill level" INTEGER NOT NULL,
PRIMARY KEY( emp_id, skill_id ),
FOREIGN KEY REFERENCES employee,
FOREIGN KEY REFERENCES skill
)
--------------------------
how does a "concatenated" key work in the above example? if you want to link to it from another table -- u have gotta have a 'concatenated' key there too? u obviously can't join to the above table if u got only emp-id..
if i use SQLCentral i can't get to see/define if the combination of both is unique or not.
if this concatenated key is a foreign key somewhere else - how is it implemented?
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Nope you do not have to do that. A composite key works just fine. The data is stored as per the composite key, so it doesn't make any sense to concatenate the two fields.
ASKER
when we have 2 fields like above example: is it normal/necessary in the sybaseDB realm or from your experience to create an additional/new field call EmpSkillID (size=both fields added up)
and call a trigger to add both fields (empID, skillID) in order to define the value. Also making EmpSkillID the primary key.