Suppose we have the usual order & order line item entities:
CREATE TABLE "order" (
id INT PRIMARY KEY,
date DATE NT NULL
);
CREATE TABLE orderlineitem (
id INT PRIMARY KEY,
orderid INT REFERENCES "order"(id),
seq INT NT NULL,
CNSTRAINT con1 UNIQUE (orderid, seq),
productid INT NT NULL,
quantity INT NT NULL,
price NUMERIC(18,4) NT NULL
);
how do we enforce things like, for example: a) each order must contain
at least 1 line item; or b) each order must have a non-zero total value;
without making INSERT painful? I'm new to triggers, so I'm thinking of
something like a "before CMMIT" trigger but there's no such thing
apparently.
Regards,
dave
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