PHP PDO Postgres与Sqlite列类型的count(*) [英] PHP PDO Postgres versus Sqlite column type for count(*)

问题描述

在此SQL语句中使用PHP PDO

Using PHP PDO with this SQL statement

SELECT count(*) FROM my_table;

返回带有Postgres的INTEGER和带有Sqlite3的STRING.也就是说，如果表中有一行，则Postgres返回(int)1，而Sqlite返回'1'.

returns an INTEGER with Postgres and a STRING with Sqlite3. That is, if there is one row in the table, Postgres returns (int)1 and Sqlite returns '1'.

这是预期的还是错误?

如果您想在家中学习，这里有一个演示脚本，我把它放在一起了.当我的PHPUnit测试通过时(使用内存中的Sqlite作为测试装置)，我实际上遇到了这个问题，但是我的应用程序使用生产的Postrgres数据库失败了.

In case you want to follow along at home, here's a demonstration script I threw together. I actually encountered this when my PHPUnit tests passed (using in-memory Sqlite as a test fixture) and but my application failed using the production Postrgres database.

<?php
function connect($dsn)
{
    try {
        $pdo = new \PDO($dsn);
    }
    catch (\PDOException $e) {
        echo 'New PDO failed: ' . $e->getMessage() . PHP_EOL;
        exit;
    }
    return $pdo;
}

function doQuery($pdo, $sql)
{
    if ( ($result = $pdo->query($sql)) === false) {
        echo "'$sql' failed: " . print_r($pdo->errorInfo(), true) . PHP_EOL;
    }
    return $result;
}

$pgo = connect('pgsql:host=localhost;dbname=postgres');
$sqo = connect('sqlite::memory:');

doQuery($pgo, 'DROP TABLE IF EXISTS public.foo');
doQuery($pgo, 'CREATE TABLE public.foo ( ii int )');
doQuery($pgo, 'INSERT INTO public.foo VALUES (42)');

doQuery($sqo, "ATTACH DATABASE ':memory:' AS public;") or die();
doQuery($sqo, 'DROP TABLE IF EXISTS public.foo');
doQuery($sqo, 'CREATE TABLE public.foo ( ii int )');
doQuery($sqo, 'INSERT INTO public.foo VALUES (42)');

$pgResult = doQuery($pgo, 'SELECT COUNT(ii) FROM foo');
echo 'Postgres: ';
var_dump($pgResult->fetchColumn());

echo 'Sqlite3: ';
$ltResult = doQuery($sqo, 'SELECT COUNT(ii) FROM foo');
var_dump($ltResult->fetchColumn());

推荐答案

这是sqlite没有数据类型的副作用.或者更确切地说，拥有所谓的动态类型系统.但很有趣

This is a side effect of sqlite not having datatypes. Or rather, having what they call the dynamic type system. But quite interestingly

SELECT TYPEOF(b) FROM ( select count(*) as b from my_table) a;

产生integer作为输出！所以很明显，从sqlite到php的翻译中丢失了一些东西.但是，这并不重要，因为php '1' + 2中给出了3.因为我们不要忘记，PHP还是动态类型化的系统.

produces integer as the output! So clearly something is being lost in translation from sqlite to php. However it doesn't really matter because in php '1' + 2 gives 3. Because let's not forget, PHP is also a dynamic typed system.

这篇关于PHP PDO Postgres与Sqlite列类型的count(*)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！