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由于 Codeigniter（恕我直言）中的分页在使用过滤器（开头字母、类别等）时缺少一些便于实施的好东西，即使我的分页功能齐全且正常工作 - 我有两个查询正在运行，它们之间的唯一区别是其中一个在末尾有 LIMIT （和 OFFSET）。需要第二个查询，因为我必须获取总行数，而我的“主”查询我无法得到它，因为它有 LIMIT，所以它返回有限的行数。

QUERY 1（“主要”查询）

SELECT art.*, songs.numsongs 
        FROM _tbl_artists AS art
        LEFT JOIN 
        (SELECT _ARTIST_ID, COUNT(*) AS numsongs 
        FROM _tbl_songs GROUP BY _ARTIST_ID) AS songs 
        ON art._ID_ORIGINAL = songs._ARTIST_ID 
        WHERE art._artist_type = 0 AND art._ARTIST_NAME LIKE 'C%' AND art.id > 0 ORDER BY art._ARTIST_NAME ASC LIMIT 20, 20

QUERY 2（这个计算行数）

SELECT art.*, songs.numsongs 
        FROM _tbl_artists AS art
        LEFT JOIN 
        (SELECT _ARTIST_ID, COUNT(*) AS numsongs 
        FROM _tbl_songs GROUP BY _ARTIST_ID) AS songs 
        ON art._ID_ORIGINAL = songs._ARTIST_ID 
        WHERE art._artist_type = 0 AND art._ARTIST_NAME LIKE 'C%' AND art.id > 0 ORDER BY art._ARTIST_NAME ASC

模型代码（它很乱，我知道:)）：

function loadArtists($type='', $letter='', $uriOffset=0, $perPage='')
{
    $letterEval = preg_match('[0-9]', $letter);
    switch($letterEval):
        case 1:
            $operator = 'REGEXP';
            $letter = "^[0-9]";
            $s = '';
            break;
        case 0:
            $operator = 'LIKE';
            $letter = "$letter";
            $s = '%';
            break;
        default: 0; break;
    endswitch;

    $query = "SELECT SQL_CALC_FOUND_ROWS art.*, songs.numsongs 
        FROM _tbl_artists AS art
        LEFT JOIN 
        (SELECT _ARTIST_ID, COUNT(*) AS numsongs 
        FROM _tbl_songs GROUP BY _ARTIST_ID) AS songs 
        ON art._ID_ORIGINAL = songs._ARTIST_ID 
        WHERE";
        if($type == 0 || $type == 1)
            $query .= " art._artist_type = $type AND";

        if($letter != '')
            $query .= " art._ARTIST_NAME $operator '$letter$s' AND";
        else
            $query .= '';

    $query .= " art.id > 0 ORDER BY art._ARTIST_NAME ASC";

    if ($uriOffset != '')
        $limited = $query . " LIMIT $uriOffset, $perPage";
    else
        $limited = $query . " LIMIT $perPage";

    $noLimit = $this->db->query($query);
    $withLimit = $this->db->query($limited);

    $numRows = $withLimit->num_rows(); 

    $resultStack = array();
    $resultStack = array($numRows);


    if($withLimit->num_rows() > 0)
    {
        $result = $withLimit->result();
        $message = '';
    }

    else
    {
        $result = NULL;
        $message = 'Nema rezultata';
    }

    array_push($resultStack, $result, $message);

    return $resultStack; //$resultStack;
}

所以我真正需要的是，与其运行这两个复杂的查询，我宁愿做一个查询，即使它变得更复杂，但我想从中获得总行数。

我读了一些关于 sql_calc_found_rows 的东西，但无法实现它，因为我完全不熟悉它，而且很多人说它给数据库带来了额外的压力，所以它应该只在极少数情况下使用。

任何帮助将不胜感激！

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1 回答 1

2

您可以执行以下操作来获取（未分页）行的总数：

（参见 SQL Fiddle 的输出）

SELECT art.*, songs.numsongs, artist_count.total
    FROM _tbl_artists AS art
    JOIN (
        SELECT COUNT(*) as total
        FROM _tbl_artists as art
        WHERE art._artist_type = 0
        AND art._ARTIST_NAME LIKE 'C%' AND art.id > 0
    ) artist_count
    LEFT JOIN (
        SELECT _ARTIST_ID, COUNT(*) AS numsongs 
        FROM _tbl_songs GROUP BY _ARTIST_ID
    ) AS songs ON art._ID_ORIGINAL = songs._ARTIST_ID 
    WHERE art._artist_type = 0
    AND art._ARTIST_NAME LIKE 'C%' AND art.id > 0
    ORDER BY art._ARTIST_NAME ASC
    LIMIT 20, 20;

第一个子查询仅使用您为搜索艺术家提供的条件并计算满足这些条件的总行数（艺术家）。我们不需要这里JOIN的_tbl_songs表，因为我们不关心这些艺术家在这个子查询中是否有任何歌曲。

于 2012-08-22T00:24:44.833 回答