问题
I am trying to create a table where the values in one column can't be greater than the next column over. For example, I am creating the following table.
CREATE TABLE Price (
PriceID INT PRIMARY KEY IDENTITY (1,1),
OriginalPrice FLOAT NOT NULL,
CurrentPrice FLOAT NOT NULL,
Discount FLOAT,
ShippingCost FLOAT NOT NULL,
Tax FLOAT NOT NULL);
And Current Price cannot be greater than OriginalPrice.
So what I tried doing was
CurrentPrice FLOAT CHECK (CurrentPrice <= OriginalPrice) NOT NULL,
But this gives me the following error:
Msg 8141, Level 16, State 0, Line 1
Column CHECK constraint for column 'CurrentPrice' references another column, table 'Price'.
Msg 1750, Level 16, State 0, Line 1
Could not create constraint. See previous errors.
Am I not allowed to reference a column in the same table?
回答1:
Just change it to a table-level constraint instead of a column constraint.
CREATE TABLE Price (
PriceID INT PRIMARY KEY IDENTITY (1,1),
OriginalPrice FLOAT NOT NULL,
CurrentPrice FLOAT NOT NULL,
Discount FLOAT,
ShippingCost FLOAT NOT NULL,
Tax FLOAT NOT NULL,
CHECK (CurrentPrice <= OriginalPrice));
You can also add it after, e.g.
ALTER TABLE Price ADD CHECK (CurrentPrice <= OriginalPrice);
--or
ALTER TABLE Price ADD CONSTRAINT CK_Price_Current_vs_Original
CHECK (CurrentPrice <= OriginalPrice);
来源:https://stackoverflow.com/questions/13390490/the-values-of-one-column-cannot-be-greater-than-another