SQL 查询在通过 phpmyadmin 进行测试时工作正常，但在 PHP PDO 中尝试相同的事情时失败

Posted 2023-02-24

【中文标题】SQL 查询在通过 phpmyadmin 进行测试时工作正常，但在 PHP PDO 中尝试相同的事情时失败

【英文标题】：SQL query works fine when testing through phpmyadmin but fails when attempting the same thing in PHP PDO

【发布时间】：2018-03-04 00:43:50

【问题描述】：

好的，来自here 上的另一个用户问题我有以下问题：

set @test = 0, @id=0, @count=0;
select m.id, max(count)
from (
select 
 @count := if(TookTest = 1 and PatientID = @id, @count+1, 0) as count,
 @test := Tooktest,
 @id := PatientID as id
from medical) as m
group by m.id
having max(count) >=2;

这在 phpmyadmin 中运行良好，但是当我在 PDO 语句中尝试相同时，它会失败并显示以下错误消息：

PDOException: SQLSTATE[HY000]: 一般错误

$sql="set @test = 0, @id=0, @count=0;
select m.id, max(count)
from (
select 
 @count := if(TookTest = 1 and PatientID = @id, @count+1, 0) as count,
 @test := Tooktest,
 @id := PatientID as id
from medical) as m
group by m.id
having max(count) >=2;";

try
    $stmt=$dbh->prepare($sql);
    if ($stmt->execute())
        $rows=$stmt->fetchall();
    
catch(PDOException $s)
    echo $s;

我是否缺少一些东西，比如你不能在 PDO 语句中设置变量？

【问题讨论】：

mysqli / pdo 不允许您在一次执行中执行多个语句。即select * from;select count from;

【参考方案1】：

再次，它不是设置变量是它试图同时运行两个查询的问题。所以我需要把上面的代码改成这样：

$sql="set @test = 0, @id=0, @count=0;";
try
    $stmt=$dbh->prepare($sql);
    $stmt->execute()
catch(PDOException $s)
    echo $s;


$sql="select m.id, max(count)
from (
select 
 @count := if(TookTest = 1 and PatientID = @id, @count+1, 0) as count,
 @test := Tooktest,
 @id := PatientID as id
from medical) as m
group by m.id
having max(count) >=2;";

try
    $stmt=$dbh->prepare($sql);
    if ($stmt->execute())
        $rows=$stmt->fetchall();
    
catch(PDOException $s)
    echo $s;

【参考方案2】：

这两个查询

set @test = 0, @id=0, @count=0;
select m.id, max(count)
from (
select 
 @count := if(TookTest = 1 and PatientID = @id, @count+1, 0) as count,
 @test := Tooktest,
 @id := PatientID as id
from medical) as m
group by m.id
having max(count) >=2;

可以重写为一个查询，因此您只需要一个 prepere 语句

  select m.id, max(count)
    from (
    select 
     @count := if(TookTest = 1 and PatientID = @id, @count+1, 0) as count,
     @test := Tooktest,
     @id := PatientID as id
    from medical) as m
    cross join ( select @test := 0, @id := 0, @count = :0 ) as init_user_params
    group by m.id
    having max(count) >=2;