如何使用在WHERE語句比symble比小於或大於用SUM功能

Question

我希望它列出的記錄，如果是的總數小於5

我得到一個錯誤：

An aggregate may not appear in the WHERE clause unless it is in sub query contained in a HAVING clause or select list , and the column being aggregated is an outer reference

我想列出在WCM103的學生，並且參加了少於5個班。

Answer 1

會是這樣的：你

WITH att 
    AS (SELECT studentID, 
      SUM(CASE WHEN attStatus = 'Yes' THEN 1 ELSE 0 END) as att_count 
     FROM attendance 
     GROUP BY studentID) 
SELECT * 
    FROM Attendance a 
INNER JOIN Student s USING (studentID) 
INNER JOIN att USING (studentID) 
WHERE att.att_count < 5 
    AND a.unitcode = 'SIT103'; 

工作？

你可以從你的學生，出席選擇列，你需要等

編輯：我沒有在我面前一個SQL接口tody所以一些SQL語句可能需要調整。

大衛，在新的信息的光，請嘗試以下操作：

WITH att 
    AS (SELECT unitcode, 
      studentID, 
      SUM(CASE WHEN attStatus = 'Yes' THEN 1 ELSE 0 END) as att_count 
     FROM attendance 
     WHERE attdate < TO_DATE('07/08/2011', 'DD/MM/YYYY') 
     GROUP BY unitcode, 
       studentID) 
SELECT * 
    FROM Student s 
INNER JOIN att USING (studentID) 
WHERE att.unitcode = 'SIT103' 
    AND att.att_count < 5; 

我的SQL * Plus現在重新運行。我只是跑：

CREATE TABLE student (
    studentid NUMBER, 
    student_name VARCHAR2(30) 
); 

CREATE TABLE attendance (
    studentid NUMBER, 
    unitcode VARCHAR2(10), 
    attdate DATE, 
    attstatus VARCHAR2(5) 
); 

INSERT INTO student VALUES (2106,'Jo Bloggs'); 
INSERT INTO student VALUES (2108,'Jo Schmoe'); 

INSERT INTO attendance VALUES (2106, 'SIT103', TO_DATE('05/06/2011', 'DD/MM/YYYY'), 'No'); 
INSERT INTO attendance VALUES (2106, 'SIT103', TO_DATE('07/07/2011', 'DD/MM/YYYY'), 'Yes'); 
INSERT INTO attendance VALUES (2106, 'SIT103', TO_DATE('10/05/2011', 'DD/MM/YYYY'), 'Yes'); 
INSERT INTO attendance VALUES (2108, 'SIT203', TO_DATE('05/05/2011', 'DD/MM/YYYY'), 'Yes'); 

WITH att 
    AS (SELECT unitcode, 
      studentID, 
      SUM(CASE WHEN attStatus = 'Yes' THEN 1 ELSE 0 END) as att_count 
     FROM attendance 
     WHERE attdate < TO_DATE('07/08/2011', 'DD/MM/YYYY') 
     GROUP BY unitcode, 
       studentID) 
SELECT studentid, 
     student_name, 
     unitcode 
    FROM Student s 
INNER JOIN att USING (studentID) 
WHERE att.unitcode = 'SIT103' 
    AND att.att_count < 5; 

，並得到：

STUDENTID STUDENT_NAME UNITCODE 
2106   Jo Schmoe SIT103 

哪個是正確的，不是嗎？

Answer 2

嘗試在下面與HAVING替換WHERE爲：

SELECT  * 
FROM   Attendance AS a INNER JOIN 
         Student AS s ON a.studentID = s.studentID 
HAVING  (SUM(CASE WHEN attStatus = 'Yes' THEN 1 ELSE 0 END) < 5) 

Answer 3

要使用擁有，您必須有一個group by子句，然後執行group by，並在聚合查詢後充當過濾器。

不確定你想要做一筆總額，但沒有看到表格中的數據，但你應該能夠在出席表中計算出是的數量，然後就會列出符合條件的那些數字

嘗試是這樣的（甲骨文的SQL語法）

SELECT s.studentname, count(*) 
    FROM student s, attendance a 
WHERE s.studentid=a.studentid 
    AND a.class='SIT108' 
    AND a.status='Y' 
GROUP BY s.studentname 
HAVING COUNT(*)<5 

或ANSI語法

SELECT s.studentname, count(*) 
    FROM student s 
    LEFT INNER JOIN attendance a 
    ON s.studentid=a.studentid 
WHERE a.class='SIT108' 
    AND a.status='Y' 
GROUP BY s.studentname 
HAVING COUNT(*)<5 

可以省略頂行的COUNT（*），以及如果你只是想的名單

SELECT s.studentname 
    FROM student s 
    LEFT INNER JOIN attendance a 
    ON s.studentid=a.studentid 
WHERE a.class='SIT108' 
    AND a.status='Y' 
GROUP BY s.studentname 
HAVING COUNT(*)<5 

添加任何額外的where子句或連接的需要