在 CakePHP3 查询中使用 MySQL 用户定义的变量 select

Question

这是我需要的 an example 个：

SELECT 
    @earnings := (`house_rent`+`conveyance`+`medical`+`dearness`+`others_allowances`) AS earnings ,
    @deductions := (`income_tax`+`pro_tax`+`emp_state_insu`+`absence_fine`+`others_deductions`) AS deductions,
    @earnings - @deductions AS net_salary 
FROM 
    salary

在我的例子中，我需要一个 SUM(Table.total) 作为单独的 salesTotal 列返回，并在 @salesTotal/@salesQuantity.

中重复使用

这是我尝试过的：

1.

$query->select([
    $query->newExpr([
        '@salesTotal := ',
        $query->func()->sum('Table.total')
    ]),
]);

这会生成 @salesTotal := AND SUM(Table.total)

2.

$query->select([
    $query->newExpr([
        '@salesTotal := ' . $query->func()->sum('Table.total')
    ]),
]);

结果 警告 (4096)：class Cake\Database\Expression\FunctionExpression 的对象无法转换为字符串

3.

$query->select([
    $query->newExpr([
        '@salesTotal := SUM(Table.total)'
    ]),
]);

正在收到 警告 (2)：array_combine(): Both parameters should have an equal number of elements CORE/src/ORM/ResultSet.php, line 527. It's 。

Answer 1

灵感来自 this answer, the idea was to have the variables declared, and then reused for calculating some other value. This approach could be valuable especially with complex calculations. I used \Cake\ORM\Query::newExpr() with an edited conjunction。

此外，根据 the MySQL doc on user-defined variables，我试着 SET 提前。

In addition, the default result type of a variable is based on its type at the beginning of the statement. This may have unintended effects if a variable holds a value of one type at the beginning of a statement in which it is also assigned a new value of a different type.

To avoid problems with this behavior, either do not assign a value to and read the value of the same variable within a single statement, or else set the variable to 0, 0.0, or '' to define its type before you use it.

这是我得到的查询：

$connection = $this->{'Example/Table'}->getConnection();
$connection->execute('SET @varSalesTotal = 0.0;');
$connection->execute('SET @varSalesQuantity = 0;');

$query = $this->{'Example/Table'}->find('all', [
    // ...
]);

$query->select([

    // calculate the @varSalesTotal variable
    // SQL: @varSalesTotal := SUM(ExampleTable.total)
    'varSalesTotalCol' => $query->newExpr([
        '@varSalesTotal',
        $query->func()->sum('ExampleTable.total'),
    ])->setConjunction(':='),

    // calculate the @varSalesQuantity variable
    // SQL: @varSalesQuantity := SUM(ExampleTable.quantity)
    'varSalesQuantityCol' => $query->newExpr([
        '@varSalesQuantity',
        $query->func()->sum('ExampleTable.quantity'),
    ])->setConjunction(':='),

    // attempt to calculate another value reusing the variables
    // SQL: @varSalesTotal/@varSalesQuantity AS calcPriceVar
    'calcPriceVar' => $query->newExpr([
        '@varSalesTotal',
        '@varSalesQuantity',
    ])->setConjunction('/'),

]);

注意：varSalesTotalCol 和 varSalesQuantityCol 键是必需的，否则我会得到

Warning (2): array_combine(): Both parameters should have an equal number of elements [CORE/src/ORM/ResultSet.php, line 527]

Warning (4096): Argument 1 passed to Cake\ORM\Entity::__construct() must be of the type array, boolean given, called in vendor/cakephp/cakephp/src/ORM/ResultSet.php on line 601 and defined [CORE/src/ORM/Entity.php, line 48]

最终结果，calcPriceVar 为空，显然这没有用。可能是因为：

The order of evaluation for expressions involving user variables is undefined. For example, there is no guarantee that SELECT @a, @a:=@a+1 evaluates @a first and then performs the assignment.

我仍在发布这个，因为我找不到任何使用 CakePHP 构建类似查询或以这种方式使用 newExpr() 的示例。弄了好久，可以作为参考。

我最终选择的工作选项是：

$query->select([
    // regular calculated columns
    'salesTotal' => $query->func()->sum('ExampleTable.total'),
    'salesQuantity' => $query->func()->sum('ExampleTable.quantity'),
    // calculate again, without reusing any previously calculated results
    'calcPrice' => $query->newExpr([
        $query->func()->sum('ExampleTable.total'),
        $query->func()->sum('ExampleTable.quantity'),
    ])->setConjunction('/'),
]);

我不喜欢我不能重用计算，如果有更好的方法，我很乐意学习。

Answer 2

根据您的建议，我将此作为使用 SET + 变量的简历：

控制器：

$weeks = $this->Facturas->find('Weeks', $options)->fetchAll('assoc');

型号：

public function findWeeks(Query $query, array $options = []) {
     $conn = ConnectionManager::get('default');
     $conn->execute('SET @row_number = 0');
     $query = 'SELECT @row_number:=@row_number + 1) AS week_number FROM weeks';
     $stmt = $conn->execute($query);
     return $stmt;
}

我正在使用 CakePHP 3.8

Answer 3

由于您没有绑定任何值，因此您可以简单地按字面意思编写这些子句，而不会有任何复杂性。像这样：

$query
    ->select(array(
        '@earnings := (`house_rent`+`conveyance`+`medical`+`dearness`+`others_allowances`) AS earnings',
        '@deductions := (`income_tax`+`pro_tax`+`emp_state_insu`+`absence_fine`+`others_deductions`) AS deductions',
        '@earnings - @deductions AS net_salary',
    ))
    ->from('salary')
;

我没有填充的 table 来测试它并确定它 return 你想要的，但它确实 return 这个结构的空数组（而不是抛出异常）使用 CakePHP：

CREATE TABLE salary (
    id INT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
    house_rent INT DEFAULT 0,
    conveyance INT DEFAULT 0,
    medical INT DEFAULT 0,
    dearness INT DEFAULT 0,
    others_allowances INT DEFAULT 0,
    income_tax INT DEFAULT 0,
    pro_tax INT DEFAULT 0,
    emp_state_insu INT DEFAULT 0,
    absence_fine INT DEFAULT 0,
    others_deductions INT DEFAULT 0
);

在 CakePHP3 查询中使用 MySQL 用户定义的变量 select

Using MySQL user-defined variables with CakePHP3 query select

mysql

cakephp

cakephp-3.0

这是我需要的 an example 个：

这是我尝试过的：