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Legal StudiesMySQL：使用 Group By 更新欄位？
要使用 GROUP BY 更新欄位，請用 ORDER BY LIMIT 與 UPDATE 命令一起使用 −
mysql> create table DemoTable2018 -> ( -> EmployeeId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> EmployeeName varchar(20), -> EmployeeSalary int -> ); Query OK, 0 rows affected (0.61 sec)
使用插入命令在表中插入某些記錄 −
mysql> insert into DemoTable2018(EmployeeName,EmployeeSalary) values('Chris',10000);
Query OK, 1 row affected (0.19 sec)
mysql> insert into DemoTable2018(EmployeeName,EmployeeSalary) values('David',12560);
Query OK, 1 row affected (0.18 sec)
mysql> insert into DemoTable2018(EmployeeName,EmployeeSalary) values('Chris',25400);
Query OK, 1 row affected (0.09 sec)使用 select 語句顯示錶中的所有記錄 −
mysql> select *from DemoTable2018;
將生成以下輸出 −
+------------+--------------+----------------+ | EmployeeId | EmployeeName | EmployeeSalary | +------------+--------------+----------------+ | 1 | Chris | 10000 | | 2 | David | 12560 | | 3 | Chris | 25400 | +------------+--------------+----------------+ 3 rows in set (0.00 sec)
這裡是要更新 MySQL 欄位的查詢 −
mysql> update DemoTable2018 -> set EmployeeSalary=EmployeeSalary+2500 where EmployeeName='Chris' -> order by EmployeeId limit 1; Query OK, 1 row affected (0.13 sec) Rows matched: 1 Changed: 1 Warnings: 0
讓我們再次檢查表記錄 −
mysql> select *from DemoTable2018;
將生成以下輸出 −
+------------+--------------+----------------+ | EmployeeId | EmployeeName | EmployeeSalary | +------------+--------------+----------------+ | 1 | Chris | 12500 | | 2 | David | 12560 | | 3 | Mike | 25400 | +------------+--------------+----------------+ 3 rows in set (0.00 sec)
更新日期： 06-04-2020
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