PHP 准备的语句与 MySQL 会话变量

Question

我目前有以下查询，它使用 UNION 联接连接两个查询和 SQL 变量来交替行在数字总和和活动计数之间的显示顺序。当我将SET行添加到查询中时，PHP文件出现错误，当我删除它们时，查询运行，但没有检索到任何值。我已经在服务器上运行了查询，它可以工作。

如何在预准备语句中使用 SQL 变量？如果不可能，我将如何重写查询以获得相同的结果？

SET @a = 0;
SET @b = 0;
SELECT * FROM(
    SELECT @a := @a + 1 AS sortOne, 1 AS sortTwo, tbl_company.comp_name AS comp_name, tbl_shift.shift_name AS shift_name,
                          SUM(tbl_short_term_programme.sun_p) AS sun_p_total, SUM(tbl_short_term_programme.sun_a) AS sun_a_total,
                          SUM(tbl_short_term_programme.mon_p) AS mon_p_total, SUM(tbl_short_term_programme.mon_a) AS mon_a_total,
                          SUM(tbl_short_term_programme.tue_p) AS tue_p_total, SUM(tbl_short_term_programme.tue_a) AS tue_a_total,
                          SUM(tbl_short_term_programme.wed_p) AS wed_p_total, SUM(tbl_short_term_programme.wed_a) AS wed_a_total,
                          SUM(tbl_short_term_programme.thu_p) AS thu_p_total, SUM(tbl_short_term_programme.thu_a) AS thu_a_total,
                          SUM(tbl_short_term_programme.fri_p) AS fri_p_total, SUM(tbl_short_term_programme.fri_a) AS fri_a_total,
                          SUM(tbl_short_term_programme.sat_p) AS sat_p_total, SUM(tbl_short_term_programme.sat_a) AS sat_a_total
                        FROM tbl_short_term_programme
                          INNER JOIN tbl_phase ON tbl_short_term_programme.phase_id = tbl_phase.phase_id
                          INNER JOIN tbl_company ON tbl_short_term_programme.company_id = tbl_company.company_id
                          INNER JOIN tbl_shift ON tbl_short_term_programme.shift_id = tbl_shift.shift_id
                        WHERE tbl_phase.phase_hash = ? AND YEARWEEK(tbl_short_term_programme.short_term_date, 2) = YEARWEEK(?, 2)
                        GROUP BY tbl_shift.shift_id, tbl_company.comp_name 
    UNION                             
    SELECT @b := @b + 1 AS sortOne, 2 AS sortTwo, tbl_company.comp_name AS comp_name, tbl_shift.shift_name AS shift_name,
                          COUNT(tbl_short_term_programme.sun_p) AS sun_p_total, COUNT(tbl_short_term_programme.sun_a) AS sun_a_total,
                          COUNT(tbl_short_term_programme.mon_p) AS mon_p_total, COUNT(tbl_short_term_programme.mon_a) AS mon_a_total,
                          COUNT(tbl_short_term_programme.tue_p) AS tue_p_total, COUNT(tbl_short_term_programme.tue_a) AS tue_a_total,
                          COUNT(tbl_short_term_programme.wed_p) AS wed_p_total, COUNT(tbl_short_term_programme.wed_a) AS wed_a_total,
                          COUNT(tbl_short_term_programme.thu_p) AS thu_p_total, COUNT(tbl_short_term_programme.thu_a) AS thu_a_total,
                          COUNT(tbl_short_term_programme.fri_p) AS fri_p_total, COUNT(tbl_short_term_programme.fri_a) AS fri_a_total,
                          COUNT(tbl_short_term_programme.sat_p) AS sat_p_total, COUNT(tbl_short_term_programme.sat_a) AS sat_a_total
                        FROM tbl_short_term_programme
                          INNER JOIN tbl_phase ON tbl_short_term_programme.phase_id = tbl_phase.phase_id
                          INNER JOIN tbl_company ON tbl_short_term_programme.company_id = tbl_company.company_id
                          INNER JOIN tbl_shift ON tbl_short_term_programme.shift_id = tbl_shift.shift_id
                        WHERE tbl_phase.phase_hash = ? AND YEARWEEK(tbl_short_term_programme.short_term_date, 2) = YEARWEEK(?, 2)
                        GROUP BY tbl_shift.shift_id, tbl_company.comp_name
) AS result ORDER BY sortOne, sortTwo
    $stmt->bind_param("ssss", $phase_hash, $formatted_date, $phase_hash, $formatted_date);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($comp_name, $shift_name, $sun_p_total, $sun_a_total, $mon_p_total, $mon_a_total, $tue_p_total,
                    $tue_a_total, $wed_p_total, $wed_a_total, $thu_p_total, $thu_a_total, $fri_p_total, $fri_a_total,
                    $sat_p_total, $sat_a_total);
    $row_array = array();
    while($stmt->fetch()) {
        $tmp = array();
        $tmp["shift_name"] = $shift_name;
        $tmp["comp_name"] = $comp_name;
        $tmp["sun_p_total"] = $sun_p_total;
        $tmp["sun_a_total"] = $sun_a_total;
        $tmp["mon_p_total"] = $mon_p_total;
        $tmp["mon_a_total"] = $mon_a_total;
        $tmp["tue_p_total"] = $tue_p_total;
        $tmp["tue_a_total"] = $tue_a_total;
        $tmp["wed_p_total"] = $wed_p_total;
        $tmp["wed_a_total"] = $wed_a_total;
        $tmp["thu_p_total"] = $thu_p_total;
        $tmp["thu_a_total"] = $thu_a_total;
        $tmp["fri_p_total"] = $fri_p_total;
        $tmp["fri_a_total"] = $fri_a_total;
        $tmp["sat_p_total"] = $sat_p_total;
        $tmp["sat_a_total"] = $sat_a_total;
        array_push($row_array, $tmp);
    }
    $stmt->close();
    echo json_encode($row_array);

Answer 1

正如 Bill Karwin 所说，您只能在预准备语句中运行一个查询。解决该问题的另一种方法是在与主查询联接的子查询中分配变量。

SELECT * FROM(
    SELECT @a := @a + 1 AS sortOne, 1 AS sortTwo, tbl_company.comp_name AS comp_name, tbl_shift.shift_name AS shift_name,
          SUM(tbl_short_term_programme.sun_p) AS sun_p_total, SUM(tbl_short_term_programme.sun_a) AS sun_a_total,
          SUM(tbl_short_term_programme.mon_p) AS mon_p_total, SUM(tbl_short_term_programme.mon_a) AS mon_a_total,
          SUM(tbl_short_term_programme.tue_p) AS tue_p_total, SUM(tbl_short_term_programme.tue_a) AS tue_a_total,
          SUM(tbl_short_term_programme.wed_p) AS wed_p_total, SUM(tbl_short_term_programme.wed_a) AS wed_a_total,
          SUM(tbl_short_term_programme.thu_p) AS thu_p_total, SUM(tbl_short_term_programme.thu_a) AS thu_a_total,
          SUM(tbl_short_term_programme.fri_p) AS fri_p_total, SUM(tbl_short_term_programme.fri_a) AS fri_a_total,
          SUM(tbl_short_term_programme.sat_p) AS sat_p_total, SUM(tbl_short_term_programme.sat_a) AS sat_a_total
        FROM tbl_short_term_programme
          INNER JOIN tbl_phase ON tbl_short_term_programme.phase_id = tbl_phase.phase_id
          INNER JOIN tbl_company ON tbl_short_term_programme.company_id = tbl_company.company_id
          INNER JOIN tbl_shift ON tbl_short_term_programme.shift_id = tbl_shift.shift_id
          CROSS JOIN (SELECT @a := 0) AS var
        WHERE tbl_phase.phase_hash = ? AND YEARWEEK(tbl_short_term_programme.short_term_date, 2) = YEARWEEK(?, 2)
        GROUP BY tbl_shift.shift_id, tbl_company.comp_name 
    UNION                             
    SELECT @b := @b + 1 AS sortOne, 2 AS sortTwo, tbl_company.comp_name AS comp_name, tbl_shift.shift_name AS shift_name,
          COUNT(tbl_short_term_programme.sun_p) AS sun_p_total, COUNT(tbl_short_term_programme.sun_a) AS sun_a_total,
          COUNT(tbl_short_term_programme.mon_p) AS mon_p_total, COUNT(tbl_short_term_programme.mon_a) AS mon_a_total,
          COUNT(tbl_short_term_programme.tue_p) AS tue_p_total, COUNT(tbl_short_term_programme.tue_a) AS tue_a_total,
          COUNT(tbl_short_term_programme.wed_p) AS wed_p_total, COUNT(tbl_short_term_programme.wed_a) AS wed_a_total,
          COUNT(tbl_short_term_programme.thu_p) AS thu_p_total, COUNT(tbl_short_term_programme.thu_a) AS thu_a_total,
          COUNT(tbl_short_term_programme.fri_p) AS fri_p_total, COUNT(tbl_short_term_programme.fri_a) AS fri_a_total,
          COUNT(tbl_short_term_programme.sat_p) AS sat_p_total, COUNT(tbl_short_term_programme.sat_a) AS sat_a_total
        FROM tbl_short_term_programme
          INNER JOIN tbl_phase ON tbl_short_term_programme.phase_id = tbl_phase.phase_id
          INNER JOIN tbl_company ON tbl_short_term_programme.company_id = tbl_company.company_id
          INNER JOIN tbl_shift ON tbl_short_term_programme.shift_id = tbl_shift.shift_id
          CROSS JOIN (SELECT @b :- 0) AS var
        WHERE tbl_phase.phase_hash = ? AND YEARWEEK(tbl_short_term_programme.short_term_date, 2) = YEARWEEK(?, 2)
        GROUP BY tbl_shift.shift_id, tbl_company.comp_name
) AS result ORDER BY sortOne, sortTwo

Answer 2

默认情况下，每次调用 mysqli_prepare() 只能运行一条 SQL 语句。

我建议在单独的语句中设置会话变量：

$mysqli->query("set @a = 0, @b = 0");

然后准备和执行你的大查询。

有些人可能会告诉你使用 mysqli_multi_query(( 函数，但你不能，因为它不支持预准备语句。

不过没关系，在一次调用中执行多个查询没有任何优势。只需在一次调用中设置变量，然后执行准备好的语句。只要使用相同的数据库连接，会话变量仍将具有其值。