MySQL更新查询-按行号

Question

I'd like to update a row in a MySQL table when a specific row number is reached

This is a little confusing since , the real row number of the record isn't a column in the table.

And there's no question of iterating over rows , since we're not iterating over an array as in mysql_fetch_array()

So , if I'd like to update - say the 3rd row of the table , what would the query be like?

I'm a noob at MySQL

Thanks a ton for your help ! :D

Answer 1

$link = mysqli_connect("localhost", "my_user", "my_password", "my_db");
$query = "SELECT MyColoumn FROM Mytable";
$result = mysqli_query($link, $query);

$row_needed = 3; //Your needed row e.g: 3rd row
for ($i=1,$i=$row_needed,$i++) {
$row = mysqli_fetch_array($result); 
}
// now we are in 3rd row
$query = "UPDATE MyColumn FROM MyTable SET MyColumn = '".$MyColumnUpdate."' WHERE MyColumn = '".$row['MyColumn']."' ";
$result = mysqli_query($link, $query);
...

Answer 2

Try this query

UPDATE 
   tbl a, 
   (Select 
       @rn:=@rn+1 as rowId, 
       tbl.* 
   from 
       tbl 
   join 
       (select @rn:=0) tmp) b
SET 
   a.columnName = <VALUE>
WHERE 
   b.rowId = <rowNumber> AND
   a.id = b.id;

NOTE The id column must be a unique one, you can use the primary key of that table...

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