限制 MySQL SELECT 结果中长文本字段的长度?
mysqlmysqli database
您可以使用 MySQL 中的 SUBSTRING() 来限制字符串的长度。语法如下
SELECT SUBSTRING(yourColumnName,1,yourIntegerValueToGetTheCharacters) as anyVariableName from yourTableName;
为了理解上述语法，让我们创建一个表。创建表的查询如下
mysql> create table limitLengthOfLongTextDemo -> ( -> sentence LONGTEXT -> ); Query OK, 0 rows affected (0.74 sec)
使用 insert 命令在表中插入一些记录。 查询语句如下
mysql> insert into limitLengthOfLongTextDemo values('This is the introduction to MySQL');
Query OK, 1 row affected (0.17 sec)
mysql> insert into limitLengthOfLongTextDemo values('PL/SQL is the extension of Structured
Query Language');
Query OK, 1 row affected (0.19 sec)
mysql> insert into limitLengthOfLongTextDemo values('Java is an Object Oriented
Programming Language');
Query OK, 1 row affected (0.20 sec)
使用 select 语句显示表中的所有记录。查询如下
mysql> select *from limitLengthOfLongTextDemo;
以下是输出 −
+------------------------------------------------------+ | sentence | +------------------------------------------------------+ | This is the introduction to MySQL | | PL/SQL is the extension of Structured Query Language | | Java is an Object Oriented Programming Language | +------------------------------------------------------+ 3 rows in set (0.00 sec)
这是获取给定值的字符的查询
mysql> select substring(sentence,1,26) as 26Characters from limitLengthOfLongTextDemo;
以下是输出 −
+----------------------------+ | 26Characters | +----------------------------+ | This is the introduction t | | PL/SQL is the extension of | | Java is an Object Oriented | +----------------------------+ 3 rows in set (0.00 sec)
