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MySQL Group by one column, but select all data

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无人共我
无人共我 2021-01-12 04:42

I\'ve got a database which contains lots of data. I would like to select all data, but Group by one column.

So for example:

column a | column b
examp
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  • 余生分开走
    2021-01-12 05:22

    All SQL systems deal in tables: rectangles of data with rows and columns. Your question asks for a result set which isn't really a rectangle of data, in the sense that it contains "header" rows and "detail" rows.

     Example:    (header row)
   - apple   (detail row)

    It's common practice to create such header / detail breakout in your client (php) software.

    Pro tip: Remember that if you don't specify ORDER BY, MySQL (and all SQLs) are permitted to return the information in your result in any convenient order. Enlarging on Gordon's fine answer, then, you might want:

     SELECT a, 
        GROUP_CONCAT(CONCAT(b, ':', 'c') ORDER BY b,c) AS bcs
   FROM t
  GROUP BY A
  ORDER BY A

    I learned this the hard way when I helped write a SQL app that was really successful. All the ordering worked great until we switched over to higher - capacity clustered access methods. Then lots of "default" ordering broke and our customers saw strange stuff until we fixed it.

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  • 再見小時候
    2021-01-12 05:41

    The example live of accordion: http://jsfiddle.net/WMUJ3/207/ Just implement in code below. ;)

    The code to mount data:

    <html>

    <head>Your page</head>

    <body>

        <div class="accordion">
            <?php echo getData() ?>
        </div>

    </body>

</html>

<?php

function getData(){

    //This get the unique values of column a
    $sql = "SELECT DISTINCT column_a FROM table";
    $result = mysql_query($sql) or die(mysql_error());

    while ($row = mysql_fetch_object($result)) {

        $html = "<h3>{$row->column_a}</h3>";

        //This get the values with column a some value
        $sql2 = "SELECT column_b FROM table WHERE column_a LIKE '%{$row->column_a}%'";
        $result2 = mysql_query($sql2) or die(mysql_error());

        $html .= '<div class="pane"><ul>';
        while ($row2 = mysql_fetch_object($result2)) {
            $html .= '<li>{$row2->column_b}</li>';
        }
        $html .= '</ul></div>';

    }

    return $html;

}

?>
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  • 日久生厌
    2021-01-12 05:46

    I think you can get what you want using group_concat():

    select a, group_concat(b)
from t
group by a;

    This will create a list of "b"s for each a. In your example:

    example    apple,pear,orange,strawberry

    You can change the separator using the SEPARATOR keyword.

    EDIT:

    You can use group_concat() multiple times:

    select a, group_concat(b) as bs, group_concat(c) as cs
from t
group by a;

    Or, combine it with concat():

    select a, group_concat(concat(b, ':', 'c')) as bcs
from t
group by a;
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