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Legal Studies獲取 MySQL 中特定列值的大小並顯示和
我們首先建立一個表 −
mysql> create table DemoTable1612 -> ( -> FirstName varchar(20), -> LastName varchar(20) -> ); Query OK, 0 rows affected (0.87 sec)
使用 insert 命令向表中插入一些記錄 −
mysql> insert into DemoTable1612 values('David','Brown');
Query OK, 1 row affected (0.75 sec)
mysql> insert into DemoTable1612 values('John','Smith');
Query OK, 1 row affected (0.21 sec)
mysql> insert into DemoTable1612 values('Bob','Taylor');
Query OK, 1 row affected (0.13 sec)使用 select 語句顯示錶中的所有記錄 −
mysql> select * from DemoTable1612;
這將產生以下輸出 −
+-----------+----------+ | FirstName | LastName | +-----------+----------+ | David | Brown | | John | Smith | | Bob | Taylor | +-----------+----------+ 3 rows in set (0.00 sec)
以下是獲取 MySQL 中選定行大小的查詢 −
mysql> select sum(char_length(FirstName)) from DemoTable1612 where LastName IN('Brown','Smith','Taylor');這將產生以下輸出 −
+-----------------------------+ | sum(char_length(FirstName)) | +-----------------------------+ | 12 | +-----------------------------+ 1 row in set (0.00 sec)
更新日期：2019 年 12 月 10 日
99 次觀看
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