Summarize the commonly used add, delete, modify and query functions in PHP

PHP is a widely used open source server-side scripting language. Its powerful database support makes it a key tool for web application development. In PHP, many functions are provided for addition, deletion, modification and query. These functions can help us operate the database more conveniently. This article will introduce some commonly used add, delete, modify and query functions in PHP.

1. Add data

1.mysql_query()

mysql_query() is one of the most commonly used functions in PHP, used to add data to the database. The SQL statement it executes must be an INSERT statement, which is used to insert a record into a table.

The following is a sample code for adding data to the database using the mysql_query() function:

//连接到MySQL数据库
$conn = mysql_connect($host, $user, $password);
mysql_select_db($database, $conn);

//定义要添加的数据
$name = "Peter";
$age  = 25;

//执行INSERT语句
$sql = "INSERT INTO persons (name, age) VALUES ('$name', '$age')";
$result = mysql_query($sql);

if (!$result) {
    echo "添加数据失败：" . mysql_error();
}

2.PDO::exec()

PDO::exec() function also Data can be added to the database. The difference between it and the mysql_query() function is that the PDO::exec() function returns the number of affected rows, while the mysql_query() function returns resource type data. When executing an INSERT statement, the PDO::exec() function returns the number of inserted records.

The following is a sample code for adding data to the database using the PDO::exec() function:

//连接到MySQL数据库
$conn = new PDO("mysql:host=$host;dbname=$database", $user, $password);

//定义要添加的数据
$name = "Peter";
$age  = 25;

//执行INSERT语句
$sql = "INSERT INTO persons (name, age) VALUES ('$name', '$age')";
$affectedRows = $conn->exec($sql);

if ($affectedRows == 0) {
    echo "添加数据失败";
}

2. Delete data

1.mysql_query()

When using the mysql_query() function to delete data, the SQL statement executed must be a DELETE statement. The following is a sample code for using the mysql_query() function to delete data:

//连接到MySQL数据库
$conn = mysql_connect($host, $user, $password);
mysql_select_db($database, $conn);

//执行DELETE语句
$sql = "DELETE FROM persons WHERE name = 'Peter'";
$result = mysql_query($sql);

if (!$result) {
    echo "删除数据失败：" . mysql_error();
}

2.PDO::exec()

The main difference between the PDO::exec() function and the mysql_query() function is It returns the number of rows affected. When executing the DELETE statement, the PDO::exec() function returns the number of deleted records.

The following is a sample code for using the PDO::exec() function to delete data:

//连接到MySQL数据库
$conn = new PDO("mysql:host=$host;dbname=$database", $user, $password);

//执行DELETE语句
$sql = "DELETE FROM persons WHERE name = 'Peter'";
$affectedRows = $conn->exec($sql);

if ($affectedRows == 0) {
    echo "删除数据失败";
}

3. Modify the data

1.mysql_query()

When using the mysql_query() function to modify data, the SQL statement executed must be an UPDATE statement. The following is a sample code for using the mysql_query() function to modify data:

//连接到MySQL数据库
$conn = mysql_connect($host, $user, $password);
mysql_select_db($database, $conn);

//执行UPDATE语句
$sql = "UPDATE persons SET age = 26 WHERE name = 'Peter'";
$result = mysql_query($sql);

if (!$result) {
    echo "修改数据失败：" . mysql_error();
}

2.PDO::exec()

PDO::exec() function can also be used to modify data, executed The SQL statement must also be an UPDATE statement. The following is an example code for using the PDO::exec() function to modify data:

//连接到MySQL数据库
$conn = new PDO("mysql:host=$host;dbname=$database", $user, $password);

//执行UPDATE语句
$sql = "UPDATE persons SET age = 26 WHERE name = 'Peter'";
$affectedRows = $conn->exec($sql);

if ($affectedRows == 0) {
    echo "修改数据失败";
}

4. Query data

1.mysql_query()

Use the mysql_query() function to query When extracting data, the SQL statement executed must be a SELECT statement. The following is a sample code for querying data using the mysql_query() function:

//连接到MySQL数据库
$conn = mysql_connect($host, $user, $password);
mysql_select_db($database, $conn);

//执行SELECT语句
$sql     = "SELECT * FROM persons WHERE age = 26";
$result  = mysql_query($sql);
$numRows = mysql_num_rows($result);

if ($numRows > 0) {
    while ($row = mysql_fetch_assoc($result)) {
        //处理查询结果
    }
} else {
    echo "没有找到数据";
}

2.PDO::query()

The PDO::query() function is used to execute a SELECT statement and return a PDOStatement object. The following is a sample code for querying data using the PDO::query() function:

//连接到MySQL数据库
$conn = new PDO("mysql:host=$host;dbname=$database", $user, $password);

//执行SELECT语句
$sql = "SELECT * FROM persons WHERE age = 26";
$result = $conn->query($sql);

$numRows = $result->rowCount();
if ($numRows > 0) {
    while ($row = $result->fetch(PDO::FETCH_ASSOC)) {
        //处理查询结果
    }
} else {
    echo "没有找到数据";
}

Summary: PHP provides many functions for adding, deleting, modifying, and querying. This article introduces some commonly used functions, including mysql_query(), PDO::exec(), PDO::query(), etc. Readers can choose the function that suits them according to their needs in actual development.

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