Question

我们可以从同一数据库和相同数据类型的两个不同表中添加两个select sql查询。这两个查询在满足where条件后从表中选择唯一的单元格。现在我想总结这两个具有相同数据类型的查询（即float类型）。如何执行添加操作：对于Ex：$ sql = 1和$ sqlNew = 2 ...我想要$ add = $ sql + $ sqlNew = 3

$sql = "SELECT num1 FROM tech WHERE name1='dsf'"; //Selecting a particular cell from table tech
$sqlNew = "SELECT num2 FROM technew WHERE name2='asd'"; //Selecting a particular cell from table technew
$add = $sql + $sqlNew; // Can this operation be perfromed?

想要从两个不同的表中添加单元格，并希望将其保存在新变量中。请告诉我如何执行上述操作。我是sql的新手。这是我的完整代码：

    <html>
<body>

<?php
$servername = "localhost";
$username = "root";
$password = "";
$dbname = "sample";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 
$add="SELECT (tech.num1 + technew.num2) as total FROM tech, technew WHERE tech.name1 = 'def' AND technew.name2 = 'asd'"; 
$result = mysqli_query($conn, $add); 
$row = mysqli_fetch_array($result, MYSQLI_ASSOC); 
echo $row['total']; 
$sql4 = "INSERT INTO finaladdition (id, finalAddTotal ) VALUES (NULL,'$row[total]')";
$conn->close();
?> 
</body>
</html>

Answer 1

您可以执行JOIN（在示例中暗示INNER JOIN）查询：

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myelement.innerHTML = mycss.getPropertyValue("background-color");

根据更多信息，您应该这样做：

SELECT (a.num1 + b.num2) as total
FROM tech a, technew b
WHERE a.name1 = 'def'
AND b.name2 = 'asd'

添加两个包含来自同一数据库的两个不同表的值的变量

1 个答案: