存储过程中的 OUT 参数声明

Question

请原谅我的问题很简单，但我无法从类似的问题中理解我必须做什么。

我有这段代码，它可以工作，但我被要求插入 CountMacro1、CountMacro2、CountMacro3、CountMacro4 的输入值，它始终为 0。我如何向 mysql 解释我希望将这些变量设置为 0？设置@CountMacro1 = 0;好像不行，为什么？谢谢大家：D

Mysql 工作台执行如下调用和选择：

set @CountMacro1 = 0;
set @CountMacro2 = 0;
set @CountMacro3 = 0;
set @CountMacro4 = 0;
call dbcbt.CountMacro_Audit_Scaduti(@CountMacro1, @CountMacro2, @CountMacro3, @CountMacro4);
select @CountMacro1, @CountMacro2, @CountMacro3, @CountMacro4;

这就是 php 中的调用：

$conn = new PDO("mysql:host=$servername;dbname=dbcbt", $username, $password);


$sql = 'CALL CountMacro_Audit_Scaduti(@CountMacro1_OUT,@CountMacro2_OUT,@CountMacro3_OUT,@CountMacro4_OUT)';
$stmt = $conn->prepare($sql);

$CountMacro1_OUT = 0;
$CountMacro2_OUT = 0;
$CountMacro3_OUT = 0;
$CountMacro4_OUT = 0;

$stmt->bindParam(1, $CountMacro1_OUT, PDO::PARAM_INT, 10);
$stmt->bindParam(2, $CountMacro2_OUT, PDO::PARAM_INT, 10);
$stmt->bindParam(3, $CountMacro3_OUT, PDO::PARAM_INT, 10);
$stmt->bindParam(4, $CountMacro4_OUT, PDO::PARAM_INT, 10);

print "Values of bound parameters _before_ CALL:\n";
print "  1: {$CountMacro1_OUT} 2: {$CountMacro2_OUT} 3: {$CountMacro3_OUT} 4: {$CountMacro4_OUT}\n";

$stmt->execute();

print "Values of bound parameters _after_ CALL:\n";
print "  1: {$CountMacro1_OUT} 2: {$CountMacro2_OUT} 3: {$CountMacro3_OUT} 4: {$CountMacro4_OUT}\n";

CREATE DEFINER=`root`@`localhost` PROCEDURE `CountMacro_Audit_Scaduti`(
OUT CountMacro1 int,
OUT CountMacro2 int,
OUT CountMacro3 int,
OUT CountMacro4 int
)
BEGIN
set @CountMacro1 = 0;
set @CountMacro2 = 0;
set @CountMacro3 = 0;
set @CountMacro4 = 0;

select count(*)
INTO CountMacro1
from t_audit
WHERE (t_audit.Data_Scadenza < NOW()) AND (t_audit.Data_Completamento ="" OR t_audit.Data_Completamento is null) AND (t_audit.Macro1= 1 OR t_audit.Macro2= 1 OR t_audit.Macro3= 1);

select count(*)
INTO CountMacro2
from t_audit
WHERE t_audit.Data_Scadenza < NOW() AND (t_audit.Data_Completamento ="" OR t_audit.Data_Completamento is null) AND (t_audit.Macro1= 2 OR t_audit.Macro2= 2 OR t_audit.Macro3= 2);

select count(*)
INTO CountMacro3
from t_audit
WHERE t_audit.Data_Scadenza < NOW() AND (t_audit.Data_Completamento ="" OR t_audit.Data_Completamento is null) AND (t_audit.Macro1= 3 OR t_audit.Macro2= 3 OR t_audit.Macro3= 3);

select count(*)
INTO CountMacro4
from t_audit
WHERE t_audit.Data_Scadenza < NOW() AND (t_audit.Data_Completamento ="" OR t_audit.Data_Completamento is null) AND (t_audit.Macro1= 4 OR t_audit.Macro2= 4 OR t_audit.Macro3= 4);

END 

Answer 1

您可以声明局部变量，然后您可以分配默认值。

CREATE PROCEDURE MYPROC(var OUT) 
BEGIN   
   DECLARE CountMacro1 INT DEFAULT 0;  
   DECLARE CountMacro2 INT DEFAULT 0;
   DECLARE CountMacro3 INT DEFAULT 0;  
   DECLARE CountMacro4 INT DEFAULT 0;
   --Your code
END;

在您的情况下，您尝试将默认值分配给@CountMacro1，即User defined variables，并且在您的查询中，您将计数分配给局部变量CountMacro1。两者都不一样。

您可以运行以下程序来查看差异

CREATE PROCEDURE prc_test ()
BEGIN
    DECLARE CountMacro1  INT DEFAULT 1;
    SET @CountMacro1  = 2;
    SELECT  CountMacro1 , @CountMacro1 ;
END;

输出

+-------------+--------------+
| CountMacro1 | @CountMacro1 |
+-------------+--------------+
| 1           | 2            |
+-------------+--------------+