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Legal Studies僅顯示包含空白的相應列的列值的 MySQL 查詢
為此，使用 TRIM() 函式。讓我們首先建立一個表 −
mysql> create table DemoTable826( FirstName varchar(100), Age int ); Query OK, 0 rows affected (0.60 sec)
使用插入命令在表中插入一些記錄。在此，我們已將某些記錄的 FirstName 設為空白 −
mysql> insert into DemoTable826 values(' ',24);
Query OK, 1 row affected (0.08 sec)
mysql> insert into DemoTable826 values(' ',22);
Query OK, 1 row affected (0.15 sec)
mysql> insert into DemoTable826 values('Chris',26);
Query OK, 1 row affected (0.12 sec)
mysql> insert into DemoTable826 values('Robert',27);
Query OK, 1 row affected (0.07 sec)使用 select 語句從表中顯示所有記錄 −
mysql> select *from DemoTable826 ;
這將生成以下輸出 −
+-----------+------+ | FirstName | Age | +-----------+------+ | Adam | 21 | | | 24 | | | 22 | | Chris | 26 | | Robert | 27 | +-----------+------+ 5 rows in set (0.00 sec)
以下是僅顯示包含空白的相應列的列值的查詢 −
mysql> select *from DemoTable826 where COALESCE(TRIM(FirstName), '') = '';
這將生成以下輸出 −
+-----------+------+ | FirstName | Age | +-----------+------+ | | 24 | | | 22 | +-----------+------+ 2 rows in set (0.00 sec)
更新日期：03-Sep-2019
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