SQL SERVER 用触发器实现在借阅或归还时自动修改图书的库存量

好的，您可以使用以下SQL Server触发器来实现在借阅或归还时自动修改图书的库存量：

CREATE TRIGGER update_book_inventory
ON book_transactions
AFTER INSERT, UPDATE
AS
BEGIN
    DECLARE @book_id int,
            @transaction_type varchar(10)

    SELECT @book_id = book_id, @transaction_type = transaction_type 
    FROM inserted

    IF @transaction_type = 'borrow'
    BEGIN
        UPDATE books
        SET inventory = inventory - 1
        WHERE book_id = @book_id
    END
    ELSE IF @transaction_type = 'return'
    BEGIN
        UPDATE books
        SET inventory = inventory + 1
        WHERE book_id = @book_id
    END
END

该触发器将在`book_transactions`表中的插入或更新操作之后执行。当`transaction_type`为'borrow'时，将从`books`表中减去库存量，当`transaction_type`为'return'时，则将库存量加1。