MySQL查询从字符串中获取最后三个字符以外的子字符串？
为此，您可以将SUBSTR与length()一起使用。
让我们首先创建一个表-
create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(20) );
以下是使用insert命令在表中插入一些记录的查询-
insert into DemoTable(FirstName) values('John');
insert into DemoTable(FirstName) values('Carol');
insert into DemoTable(FirstName) values('Robert');
insert into DemoTable(FirstName) values('Chris');
insert into DemoTable(FirstName) values('David');以下是使用select命令显示表中记录的查询-
select *from DemoTable;
这将产生以下输出-
+----+-----------+ | Id | FirstName | +----+-----------+ | 1 | John | | 2 | Carol | | 3 | Robert | | 4 | Chris | | 5 | David | +----+-----------+ 5 rows in set (0.00 sec)
以下是查询以获取删除最后3个字符的子字符串-
select substr(FirstName,1,length(FirstName)-3) from DemoTable;
这将产生以下输出-
+-----------------------------------------+ | substr(FirstName,1,length(FirstName)-3) | +-----------------------------------------+ | J | | Ca | | Rob | | Ch | | Da | +-----------------------------------------+ 5 rows in set (0.00 sec)
要获得相同的输出，可以使用以下替代查询-
select left(FirstName,length(FirstName)-3) from DemoTable;
这将产生以下输出-
+-------------------------------------+ | left(FirstName,length(FirstName)-3) | +-------------------------------------+ | J | | Ca | | Rob | | Ch | | Da | +-------------------------------------+ 5 rows in set (0.00 sec)
要获取最后三个字符，可以使用以下查询-
select substr(FirstName,-3) from DemoTable;
这将产生以下输出-
+----------------------+ | substr(FirstName,-3) | +----------------------+ | ohn | | rol | | ert | | ris | | vid | +----------------------+ 5 rows in set (0.00 sec)