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Legal Studies如何在 MySQL 中更新欄位以將值新增到現有值？
可以在 UPDATE 和 SET 命令的幫助下更新欄位以將值新增到現有值。語法如下所示 −
UPDATE yourTableName SET yourColumnName = yourColumnName+integerValueToAdd WHERE yourCondition;
為了理解以上語法，讓我們建立一個表。建立表的查詢如下 −
mysql> create table addingValueToExisting -> ( -> Id int NOT NULL AUTO_INCREMENT, -> Name varchar(30), -> GameScore int, -> PRIMARY KEY(Id) -> ); Query OK, 0 rows affected (0.58 sec)
使用 insert 命令在表中插入記錄。查詢如下 −
mysql> insert into addingValueToExisting(Name,GameScore) values('John',89);
Query OK, 1 row affected (0.11 sec)
mysql> insert into addingValueToExisting(Name,GameScore) values('Mike',56);
Query OK, 1 row affected (0.28 sec)
mysql> insert into addingValueToExisting(Name,GameScore) values('Sam',99);
Query OK, 1 row affected (0.18 sec)
mysql> insert into addingValueToExisting(Name,GameScore) values('Carol',100);
Query OK, 1 row affected (0.17 sec)
mysql> insert into addingValueToExisting(Name,GameScore) values('David',67);
Query OK, 1 row affected (0.25 sec)
mysql> insert into addingValueToExisting(Name,GameScore) values('Bob',78);
Query OK, 1 row affected (0.14 sec)使用 select 語句顯示錶中的所有記錄。查詢如下 −
mysql> select *from addingValueToExisting;
輸出如下 −
+----+-------+-----------+ | Id | Name | GameScore | +----+-------+-----------+ | 1 | John | 89 | | 2 | Mike | 56 | | 3 | Sam | 99 | | 4 | Carol | 100 | | 5 | David | 67 | | 6 | Bob | 78 | +----+-------+-----------+ 6 rows in set (0.00 sec)
更新欄位以將值新增到現有值。對於我們的示例，讓我們透過新增 10 將 100 更新為 110。查詢如下 −
mysql> update addingValueToExisting set GameScore = GameScore+10 where Id = 4; Query OK, 1 row affected (0.23 sec) Rows matched − 1 Changed − 1 Warnings − 0
檢查特定記錄是否已更新。查詢如下 −
mysql> select *from addingValueToExisting where Id = 4;
輸出如下 −
+----+-------+-----------+ | Id | Name | GameScore | +----+-------+-----------+ | 4 | Carol | 110 | +----+-------+-----------+ 1 row in set (0.00 sec)
檢視以上輸出，值 100 增加 10，即為現在的 110。
更新於: 30-Jul-2019
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