Question

这是我的表格，我想要唯一的价值，但所有的记录都是该值。

         Original Table                           output
        ---------------                     
Department EmployeeName EmployeeID     Department EmployeeName EmployeeID

------------------------------------      ------------------------------
Accounts     Raj           123           Accounts     Raj           123
Accounts     Alok          124                        Alok          124
Accounts     Amit          125                        Amit          125
Sales        Henry         263           Sales        Henry         263 
Sales        Mark          454                        Mark          454
Hr           Lusi          342           Hr           Lusi          342  
Hr           Rosy          637                        Rosy          637

Answer 1

尝试使用不同的查询来选择唯一值

点击此链接SQL/mysql - Select distinct/UNIQUE but return all columns?

Answer 2

这是一个完整演示的解决方案。

SQL：

-- data
create table t1(Department char(20), EmployeeName char(20), EmployeeID int);
insert into t1 values      
('Accounts',     'Raj',           123  ),         
('Accounts',     'Alok',          124  ),         
('Accounts',     'Amit',          125  ),       
('Sales',        'Henry',         263  ),       
('Sales',        'Mark',          454  ),       
('Hr',           'Lusi',          342  ),       
('Hr',           'Rosy',          637  );
select * from t1;

-- Query needed
SELECT 
    CASE WHEN @last_dep IS NULL OR @last_dep != Department
            THEN (@last_dep:=Department)
        WHEN @last_dep = Department
            THEN ''
        END AS Department,
    EmployeeName,
    EmployeeID
FROM t1 JOIN (SELECT @last_dep:=NULL) v;

输出：

mysql> select * from t1;
+------------+--------------+------------+
| Department | EmployeeName | EmployeeID |
+------------+--------------+------------+
| Accounts   | Raj          |        123 |
| Accounts   | Alok         |        124 |
| Accounts   | Amit         |        125 |
| Sales      | Henry        |        263 |
| Sales      | Mark         |        454 |
| Hr         | Lusi         |        342 |
| Hr         | Rosy         |        637 |
+------------+--------------+------------+
7 rows in set (0.00 sec)

mysql>
mysql> -- Query needed
mysql> SELECT
    ->     CASE WHEN @last_dep IS NULL OR @last_dep != Department
    ->             THEN (@last_dep:=Department)
    ->         WHEN @last_dep = Department
    ->             THEN ''
    ->         END AS Department,
    ->     EmployeeName,
    ->     EmployeeID
    -> FROM t1 JOIN (SELECT @last_dep:=NULL) v;
+------------+--------------+------------+
| Department | EmployeeName | EmployeeID |
+------------+--------------+------------+
| Accounts   | Raj          |        123 |
|            | Alok         |        124 |
|            | Amit         |        125 |
| Sales      | Henry        |        263 |
|            | Mark         |        454 |
| Hr         | Lusi         |        342 |
|            | Rosy         |        637 |
+------------+--------------+------------+
7 rows in set (0.00 sec)

Answer 3

更简单的方法，：格式化可以在应用程序级别完成。

select Department, GROUP_CONCAT(EmployeeName),GROUP_CONCAT(EmployeeID) from t1 group by Department;

Answer 4

SELECT Department，EmployeeName，EmployeeID FROM table_name GROUP BY Department;

查询以获取列的唯一值并重新获取其他列的值

4 个答案: