Select one row without duplicate entries

问题

In mysql table info i have :

Id , Name , City , date , status

I want to select all names from "info" Making the query

$query = mysql_query("SELECT name FROM info WHERE status = 1 ORDER BY id") 
         or die(mysql_error());

while ($raw = mysql_fetch_array($query)) 
{
  $name = $raw["name"];
  echo ''.$name.'<br>';
}

Well, the result is that it returns all the entries. I want to echo all the entries without duplicates.

Saying: under raw "name" we have inserted the name "John" 10 times.
I want to echo only one time. Is this possible?

回答1:

It's pretty simple:

SELECT DISTINCT name FROM info WHERE status = 1 ORDER BY id

The SQL keyword DISTINCT does the trick.

回答2:

try using this as your query:

SELECT DISTINCT name FROM info WHERE status = 1 ORDER BY id

to get distinct names

or as other suggested use GROUP BY

SELECT name FROM info WHERE status = 1 GROUP BY name ORDER BY id

I think the first one is more intuitive and there are no big performance difference between the two

EDIT

as the OP wants also the number of names here we go:

SELECT name,COUNT(id) AS n_names
FROM info WHERE status = 1
GROUP BY name
ORDER BY name

you can ORDER BY name or n_names depending on what you need

回答3:

Change

SELECT name FROM info WHERE status = 1 ORDER BY id

SELECT name FROM info WHERE status = 1 GROUP BY name ORDER BY id

Observe that GROUP BY was added. More about group by http://dev.mysql.com/doc/refman/5.0/en/group-by-hidden-columns.html

Edit:
for name with number of apparences try

SELECT name, count(name) FROM info WHERE status = 1 GROUP BY name ORDER BY id

回答4:

add GROUP BY name to your SQL Statment - this will only bring back one of each entry from the name column

回答5:

use GROUP BY name statement

$query = mysql_query("SELECT name FROM info WHERE status = 1 GROUP BY name ORDER BY id") or      die(mysql_error());

while ($raw = mysql_fetch_array($query)) {
                $name = $raw["name"];
                echo ''.$name.'<br>';
                }

回答6:

This works for me, returns the table names for a given database.

my $sql="select distinct table_name from COLUMNS  where table_schema='$database'"
my $sth = $dbht->prepare( $sql )
      or die "Cannot prepare SQL statement: $DBI::errstr\n";
  $sth->execute
      or die "Cannot execute SQL statement: $DBI::errstr\n";

  if ($DBI::err){

    $msg= "Data fetching terminated early by error: $DBI::errstr";

}


while (@col=$sth->fetchrow_array()){
    $table[$i]=$col[0];
    $i++;
}

回答7:

Let us say that you are sending bulk sms and you don't want to send the same message two times to the same guy John . What i discovered , is that using the trick of GROUP BY and ORDER BY at the same time works perfectly . But I don't say that its the best way . Here is how u can use it

SELECT name FROM info WHERE status = 1 GROUP BY name ORDER BY name

EDIT: This is important to note, when you need more then single column and there values are unique per row then the DISTINCT was not helping.

回答8:

$sql="SELECT DISTINCT name FROM status =1 GROUP BY name ORDER BY name";

$query = mysqli_query($conn,$sql);
<?php while ( $fire=mysqli_fetch_array($query)) { ?>
<h4><?php echo $query['name']; ?><br></h4>
<?php } ?>

来源：https://stackoverflow.com/questions/7040631/select-one-row-without-duplicate-entries

标签

mysql

sql

select

duplicates