我在努力計算有多少文章已經評分,所以我知道有多少結果要顯示在頁面上。但我似乎無法讓代碼正常工作,有人可以幫忙嗎?MySQL聚合問題
感謝您的幫助!
這是我到目前爲止。
SELECT students.*, students_essays.*, COUNT(students_essays.id)
FROM students
INNER JOIN students_essays ON students.student_id = students_essays.student_id
INNER JOIN essays_grades ON students_essays.id = essays_grades.students_essays_id
它應該看起來像我的分頁下面的代碼。
$q = "SELECT COUNT(id) FROM students_essays";
$r = mysqli_query ($mysqli, $q) or trigger_error("Query: $q\n<br />MySQL Error: " . mysqli_error($mysqli));
$row = mysqli_fetch_array ($r);
$records = $row[0];
以防萬一這是我的MySQL表。
CREATE TABLE students_essays (
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
student_id INT UNSIGNED NOT NULL,
content TEXT NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE students (
student_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
student_first_name VARCHAR(255) DEFAULT NULL,
student_last_name VARCHAR(255) DEFAULT NULL,
pass CHAR(40) NOT NULL,
PRIMARY KEY (student_id)
);
CREATE TABLE essays_grades (
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
grade_id INT UNSIGNED NOT NULL,
students_essays_id INT UNSIGNED NOT NULL,
student_id INT UNSIGNED NOT NULL,
PRIMARY KEY (id)
);
CREATE TABLE grades (
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
letter_grade VARCHAR(2) DEFAULT NULL,
grade_points FLOAT UNSIGNED NOT NULL DEFAULT 0,
PRIMARY KEY (id)
);
這是錯誤消息。
Error: 1140 - Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no GROUP columns is illegal if there is no GROUP BY clause in
它以什麼方式不起作用?一個錯誤信息會很有用 – Cfreak 2010-08-06 18:29:59