限制MySQL SELECT结果中longtext字段的长度？
您可以使用SUBSTRING()MySQL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 -> );
使用insert命令在表中插入一些记录。查询如下
mysql> insert into limitLengthOfLongTextDemo values('This is the introduction to MySQL');
mysql> insert into limitLengthOfLongTextDemo values('PL/SQL is the extension of Structured
Query Language');
mysql> insert into limitLengthOfLongTextDemo values('Java is an Object Oriented
Programming Language');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)