Condition Statement - Php Mysqli

Question

I am with Confuse with Condition ..

 global $db;

 $sql = " SELECT * FROM TEST";  

 $dbc = mysqli_query($db,$sql)


 if (!$sql || mysqli_num_rows($dbc) == 0)  {
      // rollback - Transaction
 }

 or 

 if (!$sql && mysqli_num_rows($dbc) == 0){
      // rollback - Transaction
 }

should i use (!$sql || mysqli_num_rows($dbc) == 0) OR (!$sql && mysqli_num_rows($dbc) == 0)

AS if $sql is true and mysqli_num_rows($dbc) == 0 ( false ) then too condition is False (roll-backed)

AND if $sql is false and mysqli_num_rows($dbc) == 4 ( true ) then too condition is False (roll-backed)

and if both are false then too roll-backed ..

similarly for :

$resultupdate = " UPDATE TEST SET A="NO" WHERE sid="check" ;

if((!$resultupdate) || (mysqli_affected_rows($db) == 0)) {
  // rollback - Transaction
}

or 

if((!$resultupdate) && (mysqli_affected_rows($db) == 0)){
  // rollback - Transaction
}

@ HAL9000, both are different , as "mysqli_num_rows() function returns the number of rows in a result set." — user3209031, Feb 14 '14 at 09:59
`if (!$sql)` will never fail, since $sql is a non-empty/non-zero string. — Marc B, Feb 14 '14 at 10:03

score 1 · Answer 1 · answered Feb 14 '14 at 10:10

1

Only one condition can work as you want.

if (mysqli_num_rows($dbc) == 0)  {
 // rollback - Transaction
}

answered Feb 14 '14 at 10:10

Shri

703
3
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CodeBird · Answer 2 · 2014-02-14T10:08:59.107

0

if (!$dbc || mysqli_num_rows($dbc) == 0)  {
  // rollback - Transaction
}

That's true you're telling php if the query didn't run or it returned 0 rows roll back. meaning in case 1 of these 2 is true you're rolling back

if (!$dbc && mysqli_num_rows($dbc) == 0){
  // rollback - Transaction
}

This, you're telling php that both should be true to roll back. if only one is true what's inside this if won't run. That's not what you want.

$resultupdate = " UPDATE TEST SET A='NO' WHERE sid='check" ;
$update_query=mysqli_query($db, $resultupdate);
if((!$update_query) || (mysqli_affected_rows($update_query) == 0)) {
  // rollback - Transaction
}

for the update, you're testing if the query didn't run, or didn't affect any rows you roll back.

edited Feb 14 '14 at 10:08

answered Feb 14 '14 at 10:03

CodeBird

3,883
2
20
35

and what in this case: $resultupdate = " UPDATE TEST SET A="NO" WHERE sid="check" ; if((!$resultupdate) || (mysqli_affected_rows($db) == 0)) { // rollback - Transaction } or if((!$resultupdate) && (mysqli_affected_rows($db) == 0)){ // rollback - Transaction } – user3209031 Feb 14 '14 at 10:06
1

what @Prix is saying is right, you don't need to test $dbc you just need to test num_rows and affected_rows. I am just clearing your confusion with the && and || – CodeBird Feb 14 '14 at 10:10
hmm yes for UPDATE ... i am check if query didn't run or didn't get effect due to some reason ..hence it will be rollback – user3209031 Feb 14 '14 at 10:27

Condition Statement - Php Mysqli

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