Select 一列中值的一部分并将其复制到另一列 - sql 查询

Question

I have the following sql query that needs to be fixed to trim any whitespace (beginning and end) of the selection. I also need it to delete the "lastname" part from the firstname column:

UPDATE customer_address_entity
   SET lastname = RIGHT(firstname,LENGTH(firstname)-LOCATE(' ',firstname)) 
 WHERE lastname = ''

For instance if the column "firstname" has "Jo de blog " in it and "lastname" column is empty I want the "firstname" column to contain "Jo" and the "lastname" column to contain "de Blog"

Answer 1

I would apporach it so.

When the firstname has 2 surnames it would take the last two When the firstname has 1 surnames it would take also only the last With increasing number of words in firstname. you need a more sophisticated algorithm to find the right index

CREATE TABLE customer_address_entity ( `id`INT, `firstname` varchar(25), `lastname` varchar(25) ); INSERT INTO customer_address_entity (`id`,`firstname`, `lastname`) VALUES (1,'Jo de blog ',''),(2,'Jo blog ',''),(3,'test2','test2');

 SELECT * FROM customer_address_entity

 id | firstname | lastname -: |:---------- |:------- 1 | Jo de blog | 2 |  Jo blog | 3 |  test2 | test2

 UPDATE `customer_address_entity` SET `lastname` = TRIM(SUBSTRING_INDEX(TRIM(`firstname`), " ", IF(LENGTH(TRIM(`firstname`)) - LENGTH(REPLACE(TRIM(`firstname`), ' ', '')) > 1,-2,-1))), firstname = TRIM(SUBSTRING_INDEX(TRIM(`firstname`), " ", 1)) WHERE `lastname` = '';

 SELECT * FROM customer_address_entity

 id | firstname | lastname -: |:-------- |:------- 1 | Jo | de blog 2 | Jo | blog 3 | test2 | test2

db<>fiddle here

Answer 2

This is a bit tricky, because your expression would not produce the expected results if the string starts with a space.

I would use:

substring(trim(firstname), locate(' ', trim(firstname)) + 1)

This basically starts by removing leading and trailing spaces from the string, then selects everything after the first space within the string.

In your update statement:

UPDATE `customer_address_entity` 
SET `lastname` = substring(trim(firstname), locate(' ', trim(firstname)) + 1)
WHERE `lastname` = ''

If there may be multiple spaces between the first name and last name, then you can trim() the resulting string too:

trim(substring(trim(firstname), locate(' ', trim(firstname)) + 1))