7.3.2.3 Executing statements

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Statements can be executed with the mysqli::query, mysqli::real_query and mysqli::multi_query. The mysqli::query function is the most common, and combines the executing statement with a buffered fetch of its result set, if any, in one call. Calling mysqli::query is identical to calling mysqli::real_query followed by mysqli::store_result.

Example 7.13 Executing queries

<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT)");

Buffered result sets

After statement execution, results can be either retrieved all at once or read row by row from the server. Client-side result set buffering allows the server to free resources associated with the statement's results as early as possible. Generally speaking, clients are slow consuming result sets. Therefore, it is recommended to use buffered result sets. mysqli::query combines statement execution and result set buffering.

PHP applications can navigate freely through buffered results. Navigation is fast because the result sets are held in client memory. Please, keep in mind that it is often easier to scale by client than it is to scale the server.

Example 7.14 Navigation through buffered results

<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT)");
$mysqli->query("INSERT INTO test(id) VALUES (1), (2), (3)");
$result = $mysqli->query("SELECT id FROM test ORDER BY id ASC");
echo "Reverse order...\n";
for ($row_no = $result->num_rows - 1; $row_no >= 0; $row_no--) {
    $result->data_seek($row_no);
    $row = $result->fetch_assoc();
    echo " id = " . $row['id'] . "\n";
}
echo "Result set order...\n";
foreach ($result as $row) {
    echo " id = " . $row['id'] . "\n";
}

The above example will output:

Reverse order...
 id = 3
 id = 2
 id = 1
Result set order...
 id = 1
 id = 2
 id = 3

Unbuffered result sets

If client memory is a short resource and freeing server resources as early as possible to keep server load low is not needed, unbuffered results can be used. Scrolling through unbuffered results is not possible before all rows have been read.

Example 7.15 Navigation through unbuffered results

<?php
$mysqli->real_query("SELECT id FROM test ORDER BY id ASC");
$result = $mysqli->use_result();
echo "Result set order...\n";
foreach ($result as $row) {
    echo " id = " . $row['id'] . "\n";
}

Result set values data types

The mysqli::query, mysqli::real_query and mysqli::multi_query functions are used to execute non-prepared statements. At the level of the MySQL Client Server Protocol, the command COM_QUERY and the text protocol are used for statement execution. With the text protocol, the MySQL server converts all data of a result sets into strings before sending. This conversion is done regardless of the SQL result set column data type. The mysql client libraries receive all column values as strings. No further client-side casting is done to convert columns back to their native types. Instead, all values are provided as PHP strings.

Example 7.16 Text protocol returns strings by default

<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT, label CHAR(1))");
$mysqli->query("INSERT INTO test(id, label) VALUES (1, 'a')");
$result = $mysqli->query("SELECT id, label FROM test WHERE id = 1");
$row = $result->fetch_assoc();
printf("id = %s (%s)\n", $row['id'], gettype($row['id']));
printf("label = %s (%s)\n", $row['label'], gettype($row['label']));

The above example will output:

id = 1 (string)
label = a (string)

It is possible to convert integer and float columns back to PHP numbers by setting the MYSQLI_OPT_INT_AND_FLOAT_NATIVE connection option, if using the mysqlnd library. If set, the mysqlnd library will check the result set meta data column types and convert numeric SQL columns to PHP numbers, if the PHP data type value range allows for it. This way, for example, SQL INT columns are returned as integers.

Example 7.17 Native data types with mysqlnd and connection option

<?php
mysqli_report(MYSQLI_REPORT_ERROR | MYSQLI_REPORT_STRICT);
$mysqli = new mysqli();
$mysqli->options(MYSQLI_OPT_INT_AND_FLOAT_NATIVE, 1);
$mysqli->real_connect("example.com", "user", "password", "database");
$mysqli->query("DROP TABLE IF EXISTS test");
$mysqli->query("CREATE TABLE test(id INT, label CHAR(1))");
$mysqli->query("INSERT INTO test(id, label) VALUES (1, 'a')");
$result = $mysqli->query("SELECT id, label FROM test WHERE id = 1");
$row = $result->fetch_assoc();
printf("id = %s (%s)\n", $row['id'], gettype($row['id']));
printf("label = %s (%s)\n", $row['label'], gettype($row['label']));

The above example will output:

id = 1 (integer)
label = a (string)

See also

mysqli::__construct

mysqli::options

mysqli::real_connect

mysqli::query

mysqli::multi_query

mysqli::use_result

mysqli::store_result