如何替换多列中存在的值？

Question

I have a database table foo and I want to replace null values present in specific columns with empty string. For removing null values present in particular column x , I would do like

update foo set x = '' where x is null;

Is there anyway I would do like,

update foo set x,y,z = '' where x,y,z is null; 

Answer 1

You can:

set 
   x = case when x is null then '' else x,
   y = case when y is null then '' else y,
   z = case when z is null then '' else z
   ...

Answer 2

This will update all rows, where any of columns x , y or z has NULL value and uses COALESCE function to modify values only in columns where value is NULL:

UPDATE
    foo
SET
    x = COALESCE(x, ''),
    y = COALESCE(y, ''),
    z = COALESCE(z, '')
WHERE
    NULL IN (x, y, z)

Answer 3

Is simpler to do this:

UPDATE foo SET x='', y='', z='' WHERE x IS NULL AND y IS NULL AND z IS NULL

Or this one if you want to edit only the values that are NULL

UPDATE foo SET x = IF(x IS NULL, '', x), y = IF(y IS NULL, '', y) ...

Answer 4

you should try this

UPDATE foo SET x ="", y = "", z = "" WHERE x is NULL and y is NULL and z is NULL