What types of MySQL query statements are there in PHP?

MySQL query statement types in PHP include: SELECT: Retrieve data from the table. WHERE: Filter SELECT results based on conditions. INSERT: Insert new records into the table. UPDATE: Update an existing record. DELETE: Delete records from the table.

MySQL query statement type in PHP

MySQL query statement is a command that interacts with the MySQL database and queries data. PHP provides a variety of functions to execute MySQL queries, and each function corresponds to different types of query statements.

SELECT statement

The SELECT statement is used to retrieve data from a database table. The syntax is as follows:

$result = $conn->query("SELECT * FROM table_name");

WHERE clause

The WHERE clause is used to filter results based on specific criteria. The syntax is as follows:

$result = $conn->query("SELECT * FROM table_name WHERE condition");

INSERT statement

The INSERT statement is used to insert new records into a database table. The syntax is as follows:

$conn->query("INSERT INTO table_name (column1, column2) VALUES (value1, value2)");

UPDATE statement

The UPDATE statement is used to update existing records in a database table. The syntax is as follows:

$conn->query("UPDATE table_name SET column1 = value1 WHERE condition");

DELETE statement

The DELETE statement is used to delete records from a database table. The syntax is as follows:

$conn->query("DELETE FROM table_name WHERE condition");

Practical case

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

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
} 

// 查询所有记录
$result = $conn->query("SELECT * FROM users");

// 输出结果
if ($result->num_rows > 0) {
  // 输出每行数据
  while($row = $result->fetch_assoc()) {
    echo "id: " . $row["id"] . " - Name: " . $row["name"] . " - Email: " . $row["email"] . "<br>";
  }
} else {
  echo "0 results";
}

// 关闭连接
$conn->close();
?>

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