PHP tips for using the PDO abstraction layer to get query results

This article mainly introduces the use of the PDO abstraction layer to obtain query results, combined with examples of PHP using the PDO abstraction layer to obtain query results of three common methods and related functions of the use of skills, the need for friends can refer to the next

This example describes how PHP uses the PDO abstraction layer to get query results. Share to everyone for your reference, as follows:

PHP uses the PDO abstraction layer to get query results, there are 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); $res->setfetchmode (Pdo::fetch_num ); Digital Index mode while ($row = $res->fetch ()) {Print_r ($row);}? >

(2) pdo->exec () Processing SQL

<?php//pdo->exec () Handles sql$psql= "INSERT into user (ID, username) VALUES (', ' Zhang San ')"; $db->setattribute (pdo::attr _errmode, pdo::errmode_exception); $res = $db->exec ($psql); Echo $res;? >

(3) PDO::p repare () Preprocessing execution query

<?php//pdo::p Repare () preprocessing executes the query $psql= "SELECT * from user", $res = $db->prepare ($psql), $res->execute (), while ($ row = $res->fetchall ()) {Print_r ($row);}? >

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

Pdo::case_lower --Force column names to be lowercase
pdo::case_natural --column names are in the original way
Pdo::case_upper --Force column name to uppercase

setFetchModemethod to set the type of return value that gets the result set, with the following common parameters:

PDO::FETCH_ASSOC --Associative array form
Pdo::fetch_num --Digital Index array form
Pdo::fetch_both --both array form, this is the default
pdo::fetch_obj -in the form of an object, similar to the previous mysql_fetch_object ()

The above summarizes the following:

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

PDO->query() -Process an SQL statement and return a "pdostatement"
PDO->exec() -Processes an SQL statement and returns the number of entries affected

PDO::prepare()It is primarily a preprocessing operation that requires a $rs->execute () to execute the SQL statement inside the preprocessing

Finally, two commonly used functions are introduced:

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

<?php$psql= "SELECT * from user"; $res = $db->query ($psql);//Gets the second field result in the specified record $col = $res->fetchcolumn (1); echo $ Col;? >

(2) fetchAll() get data from a result set and store it in an associative array

<?php$psql= "SELECT * from user", $res = $db->query ($psql), $res _arr = $res->fetchall ();p rint_r ($res _arr);? >

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