Question

我想使用if else条件基于一个列值更新两列。如果col1为空，则通过添加随机数更新col2。否则通过添加随机数来更新col1。

我正在尝试这种方式，但是语法错误。

$query = "UPDATE table SET IF(col1='', col2=col2+FLOOR($min+(RAND()*($max-$min+1))), col1=col1+FLOOR($min+(RAND()*($max-$min+1)))) WHERE id >= $id";

请参阅并建议任何可行的方法。感谢

Answer 1

您对MySQL中的IF()的理解有点偏离：它是一个控制流功能，而不是一个构造。

这意味着它不是例如控制要更新的列，但要写入哪个值。

因此，您需要以某种方式重新组合，这使得SET的列不变，同时使值变量。如果不满足此列的条件，我们只需重新分配旧值即可实现此目的。

UPDATE table SET 
  col2=IF(col1='', col2+FLOOR($min+(RAND()*($max-$min+1))), col2),
  col1=IF(col1='', col1, col1+FLOOR($min+(RAND()*($max-$min+1)))) 
WHERE id >= $id

修改

从评论开始：如果你想在col1上选择 etiher 空字符串或 null，你必须选择它：

UPDATE table SET col2=IF(col1='' OR col1 IS NULL, col2+FLOOR($min+(RAND()*($max-$min+1))), col2), col1=IF(col1='' OR col1 IS NULL, col1, col1+FLOOR($min+(RAND()*($max-$min+1)))) WHERE id >= $id

编辑2

如果col2不仅可以是空字符串，还可以是null，则需要再次测试它：

UPDATE table SET col2=IF(col1='' OR col1 IS NULL, IFNULL(col2,0)+FLOOR($min+(RAND()*($max-$min+1))), col2), col1=IF(col1='' OR col1 IS NULL, col1, col1+FLOOR($min+(RAND()*($max-$min+1)))) WHERE id >= $id

Answer 2

//hi i just try this logic on my "mysql" may be it work on your system....
//plz take a llok to the logic i try


//i don't know about the case condition but i try to help and check that is it working on your function..


//here i select the whole table row with true condition 
//here i have single row which set true condition
$q = "select * from table where id>=".$id;
$r = mysql_query($q);


//i take one row at a time with ture contition and update values by checking column is empty or not 
//this llop run till the values are there  with true condition in select query
while($ro = mysql_fetch_array($r)){

//for every row in loop i check the condition that col1 is empty, if it is then i update col 2
if($ro['col1']==""){
$q_update = "update table set col2=".$rand." where id>=".$ro['id'];
$r_update = mysql_query($q_update);
}
//for every row in loop i check the condition that col1 is empty, if it is not then i update col1
else{
$q_update = "update table set col1=".$rand." where id>=".$ro['id'];
$r_update = mysql_query($q_update);
}


}//while loop ends here

IF ELSE条件在UPDATE查询中不起作用

2 个答案: