[英]MySQL - How to control `numeric` column of one table from another table
我有以下内容:
book(book_id,book_name,quantity)
donor(book_id)
acquisition(donor_id,book_id,booksDonated)
当我在采集中插入数据时, booksDonated
的值必须更新为给定book_id
的quantity
。 我尝试学习触发器,但事实证明,由于我在PHP中工作,因此它无法传递变量。
如何同时插入和更新(使用表的给定数据)。
PS。 如果复杂,请添加查询。
这是一个更完整的答案。 首先,您需要在数据库中创建以下表结构(创建表,主键和自动增量字段)。
CREATE TABLE IF NOT EXISTS `acquisition` (
`acquistion_id` bigint(20) NOT NULL,
`donor_id` bigint(20) NOT NULL,
`book_id` bigint(20) NOT NULL,
`booksDonated` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `book` (
`book_id` bigint(20) NOT NULL,
`book_name` varchar(255) NOT NULL,
`quantity` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE IF NOT EXISTS `donor` (
`donor_id` bigint(20) NOT NULL,
`name` varchar(255) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
ALTER TABLE `acquisition` ADD PRIMARY KEY (`acquistion_id`);
ALTER TABLE `book` ADD PRIMARY KEY (`book_id`);
ALTER TABLE `donor` ADD PRIMARY KEY (`donor_id`);
ALTER TABLE `acquisition` MODIFY `acquistion_id` bigint(20) NOT NULL AUTO_INCREMENT;
ALTER TABLE `book` MODIFY `book_id` bigint(20) NOT NULL AUTO_INCREMENT;
ALTER TABLE `donor` MODIFY `donor_id` bigint(20) NOT NULL AUTO_INCREMENT;
现在,基于此结构,您可以使用以下功能
添加书籍添加捐赠者(示例中为2个不同的捐赠者)添加书籍的获取
function addBook($con, $name)
{
$id = -1;
$name = mysqli_real_escape_string($con, $name);
$query = "INSERT INTO `book` (`book_id`, `book_name`, `quantity`) VALUES (NULL, '$name', '0');";
mysqli_query($con, $query);
if (mysqli_error($con) == 0)
{
$id = mysqli_insert_id($con);
}
return $id;
}
function addDonor($con, $name)
{
$id = -1;
$name = mysqli_real_escape_string($con, $name);
$query = "INSERT INTO `donor` (`donor_id`, `name`) VALUES ('1', '$name');";
mysqli_query($con, $query);
if (mysqli_error($con) == 0)
{
$id = mysqli_insert_id($con);
}
return $id;
}
function addAcquisition($con, $book_id, $donor_id, $quantity)
{
$id = 0;
$book_id = intval($book_id);
$donor_id = intval($donor_id);
$quantity = intval($quantity);
$query = "INSERT INTO `acquisition` (`acquistion_id`, `donor_id`, `book_id`, `booksDonated`) VALUES (NULL, '{$donor_id}', '{$book_id}', '{$quantity}');";
mysqli_query($con, $query);
if (mysqli_error($con) != 0)
{
$id = -1;
}
//This SQL updates the current book count with the newly donated quantity, so they stay in sync.
$query = "UPDATE `book` SET `quantity` = (`quantity` + '{$quantity}') WHERE `book_id` = '{$book_id}';";
mysqli_query($con, $query);
if (mysqli_error($con) == 0)
{
$id = mysqli_insert_id($con);
}
return $id;
}
现在,使用这些功能,您可以创建一本书,一个或多个捐赠者及其收购。
// Fill your DB values here
$host = '';
$username = '';
$password = '';
$database = '';
// Connect to the DB
$con = mysqli_connect($host, $username, $password, $database);
// Add a book. $book_id contains the new book's ID
$book_id = addBook($con, 'This is the book\'s name');
// Add a donor. $book_id contains the new donor's ID
$donor1_id = addDonor($con, 'This is the first Donor\'s name');
// Add another book. $book_id contains the second donor's ID
$donor2_id = addDonor($con, 'This is the second Donor\'s name');
addAcquisition($con, $book_id, $donor1_id, 5);
addAcquisition($con, $book_id, $donor2_id, 10);
// After running this code, there'll be 15 in the quantity field (5 from Donor 1 + 10 from Donor 2) and 2 acquistion records
您可以使用UPDATE
查询,如下所示:
UPDATE book SET Quantity = Quantity + 'BOOKSDONATED' WHERE book_id = ID
这样,您可以将BOOKSDONATED图书(捐助者提供的图书数量)添加到book_id = ID的现有图书数量中
然后,您使用books_Id和donor_Id在获取表上插入一条记录。
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