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答案

【问题标题】：SQL query works fine when testing through phpmyadmin but fails when attempting the same thing in PHP PDOSQL 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
【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;

标签： php mysql variables pdo phpmyadmin

【解决方案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;
}

【讨论】：

【解决方案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;

【讨论】：