Replace() function

grammar
REPLACE ( string_expression , string_pattern , string_replacement )

Parameters

string_expression String expression to search .string_expression It can be character or binary data type .
string_pattern Is the substring to find .string_pattern It can be character or binary data type .string_pattern It cannot be an empty string ('').
string_replacement Replace string .string_replacement It can be character or binary data type .

Return type
If the data type of one of the input parameters is nvarchar, Then return to nvarchar; otherwise REPLACE return varchar.
If any parameter is NULL, Then return to NULL.

It's all Mandarin , Not easy to understand ！ Turn into vernacular ：

REPLACE(String,from_str,to_str) namely ： take String All of the from_str Replace with to_str.

One 、 Prepare the experimental environment

1.1 Create table ：

CREATE TABLE `test_tb` (                                                 
`id` int(10) unsigned NOT NULL auto_increment COMMENT ' The primary key increases automatically ',  
`name` char(30) default NULL COMMENT ' full name ',                         
`address` char(60) default NULL COMMENT ' Address ',                      
`country` char(200) default NULL COMMENT ' Country ',                     
PRIMARY KEY  (`id`)                                                    
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COMMENT=' The test table '  

1.2 insert data ：
 

insert into test_tb(name,address,country) values
('zhangsan',' Beijing   Chaoyang District ',' China '),
('lisi',' Shanghai   Pudong district ',' China '),
('wangwu',' Zhengzhou Jinshui District ',' China '),
('zhaoliu',' Kowloon, Hong Kong ',' Hong Kong, China, '),
('Q7',' California beef ',' The United States '),
('wangba',' New Kyushu Island ',' Japan ')

 

Two 、 Search for replacement

2.1 take address In the field “ District ” Replace with “ Vomit ” Show , as follows

 

select *,replace(address,' District ',' Vomit ') AS rep  from test_tb

2.2 take address In the field “ Nine ” Replace with “ Ten ” Show , as follows

 

select *,replace(address,' Nine ',' Ten ') AS rep from test_tb  where id in (4,6)

summary ：

I think I mentioned earlier Use IF(expr1,expr2,expr3) And CASE...WHEN...THEN...END The alias display of query results can be realized, but the difference is ： These two are the alias display of the query result value as a whole , and replace You can replace and display the local string of the query result ( Output ).

3、 ... and 、 Update and replace

3.1 take address In the field “ In the east ” Replace with “ In the west ” , as follows
update test_tb set address=replace(address,' In the east ',' In the west ') where id=2

summary ： Update and replace the local string in the field .

Four 、 Insert replace

4.1 take id=6 Of name The field value is changed to wokou
replace into test_tb VALUES(6,'wokou',' New Kyushu Island ',' Japan ')

summary ： Go to the table “ Replace insert ” A piece of data , If there is no in the original table id=6 This data is inserted as new data ( amount to insert into effect ); If there is... In the original table id=6 This data is replaced ( amount to update effect ). For fields that are not specified, the default value is inserted .