如何在UPDATE查询MYSQL中合并具有相同ID的两行

Question

I have a table with addresses and postcodes in different rows but linked by an id column.

CURRENT STATE

id addressLabel addressValue
22 home address xxxxx
22 home postcode yyyy yyyy

DESIRED STATE

id addressLabel addressValue
22 home address xxxxxx, yyyy yyy

I want to concatenate the two rows with the same id into the addressValue column with a comma separator (then delete the postcode). I have seen plenty of examples using SELECT but I can't see how they would work with UPDATE.

Answer 1

You can use a selfjoin in the UPDATE statement:

update mytable a
join mytable p using(id)
set a.addressValue = concat(a.addressValue, ', ', p.addressValue)
where a.id = 22
  and a.addressLabel = 'home address'
  and p.addressLabel = 'home postcode';

delete from mytable
where id = 22
  and addressLabel = 'home postcode';

Demo: http://sqlfiddle.com/#!9/649ef3/1

Remove the conditions id = 22 if you want to affect the full table.