PHP Sample Method for Using PDO Abstraction Layer to Get Query Results

This article illustrates how PHP uses PDO abstraction layer to obtain query results. Share it for your reference, as follows:

PHP uses PDO abstraction layer to obtain query results in three main ways:

(1) PDO:: query () query.

Look at the following php code:

<?php
//PDO::query() Query 
$psql="SELECT * FROM user";
$res = $db->query($psql);
$res->setFetchMode(PDO::FETCH_NUM); // Digital indexing mode 
while ($row = $res->fetch()){
print_r($row);
}
?>

(2) PDO- > exec () Processes sql

<?php
//PDO->exec() Deal with sql
$psql="INSERT INTO user(id , username) values('' , ' Zhang 3')";
$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$res = $db->exec($psql);
echo $res;
?>

(3) PDO:: prepare () preprocessing executes queries

<?php
//PDO::prepare() Preprocessing executes queries 
$psql="SELECT * FROM user";
$res = $db->prepare($psql);
$res->execute();
while ($row = $res->fetchAll()) {
print_r($row);
}
?>

setAttribute() The method is to set the properties, and the common parameters are as follows:

PDO:: CASE_LOWER--Force column names to be lowercase
PDO:: CASE_NATURAL--Column name as original
PDO:: CASE_UPPER--Force column name to uppercase

setFetchMode Method to set the type of return value to get the result set. The common parameters are as follows:

PDO:: FETCH_ASSOC--associative array form
PDO:: FETCH_NUM--Number index array form
PDO:: FETCH_BOTH--Both in array form, which is the default
PDO:: FETCH_OBJ--In the form of an object, similar to the previous mysql_fetch_object ()

The above is summarized as follows:

Query operations are mainly PDO::query() , PDO::exec() , PDO::prepare() .

PDO->query() --Processes 1 SQL statement and returns 1 "PDOStatement"
PDO->exec() --Processes 1 SQL statement and returns the number of entries affected

PDO::prepare() It is mainly a preprocessing operation, which needs to be passed through $rs- > execute () to execute the SQL statement in the preprocessing

Finally, two commonly used functions are introduced:

(1) fetchColumn() Get the result of 1 field in the specified record, and the default is the first field!

<?php
$psql="SELECT * FROM user";
$res = $db->query($psql);
// Gets the number in the specified record 2 Field results 
$col = $res->fetchColumn(1);
echo $col;
?>

(2) fetchAll() Get data from 1 result set and store it in associative array

<?php
$psql="SELECT * FROM user";
$res = $db->query($psql);
$res_arr =$res->fetchAll();
print_r($res_arr);
?>

For more readers interested in PHP related content, please check the topics on this site: "Summary of PHP database operation skills based on pdo", "Summary of php+Oracle database programming skills", "Encyclopedia of PHP+MongoDB database operation skills", "Introduction to php object-oriented programming", "Usage summary of php string (string)", "Introduction to php+mysql database operation skills" and "Summary of php common database operation skills"

I hope this article is helpful to everyone's PHP programming.