Question

我正在尝试加入另一个领域的独特领域。

示例：tbl.Class中有多个行分类在column.Teacher下，具有相同的值。我想在column.Teacher中加入一个DISTINCT值到另一个表中的column.Teacher_Course（tbl.Course）。

以下是我的想法，但不是只从tbl.Class中检索一个值，而是获得多个连接。

SELECT distinct(Teacher.JohnJoe)
FROM  tbl.Class

RIGHT OUTER JOIN tbl.Course ON Course.Teacher_Course = Class.Teacher

Answer 1

您也可以尝试使用GROUP BY子句：

SELECT Teacher.JohnJoe
FROM  tbl.Class
RIGHT OUTER JOIN tbl.Course ON Course.Teacher_Course = Class.Teacher  
GROUP BY Teacher.JohnJoe

Answer 2

简历：

tbl.Class中的多位老师
tbl.Course的单身教师
结果应该从tbl.Class为tbl.Class中的每个记录提供一位教师

我的SQL解释：

DECLARE @class TABLE ([id] int, [teacher] nvarchar(20))
DECLARE @course TABLE ([id] int, [course] nvarchar(20), [teacher_course] nvarchar(20))

INSERT INTO @class ([id], [teacher]) VALUES (1, 'Teacher 1')
INSERT INTO @class ([id], [teacher]) VALUES (2, 'Teacher 2')
INSERT INTO @class ([id], [teacher]) VALUES (3, 'Teacher 3')
INSERT INTO @class ([id], [teacher]) VALUES (4, 'Teacher 4')
INSERT INTO @class ([id], [teacher]) VALUES (5, 'Teacher 1')

INSERT INTO @course ([id], [course], [teacher_course]) VALUES (1, 'Course 1', 'Teacher 1')
INSERT INTO @course ([id], [course], [teacher_course]) VALUES (2, 'Course 2', 'Teacher 4')

SELECT 
    [co].[id],
    [co].[course],
    [cl].[teacher]
FROM  @course [co]
INNER JOIN @class [cl] ON [co].[teacher_course] = [cl].[teacher]
GROUP BY
    [co].[id],
    [co].[course],
    [cl].[teacher]

结果是：

[id]  [course]  [teacher]
1     Course 1  Teacher 1
2     Course 2  Teacher 4

SQL Distinct Join

2 个答案: