SQL Server 2017

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CREATE TABLE employee
    ([c_name] varchar(10), [name] varchar(40))
;
    
INSERT INTO employee
    ([c_name], [name])
VALUES
    (NULL, 'name with c_name null'),
    (NULL, 'name with c_name null 1'),
    ('      ', 'name with c_name empty')
;
SELECT * FROM EMPLOYEE

c_name
name

null
name with c_name null

null
name with c_name null 1

name with c_name empty

select case ltrim(rtrim(c_name)) when '' then name else c_name end as name from employee
select case c_name when '' then name else c_name end as name from employee

name

null

null

name with c_name empty

name

null

null

name with c_name empty

select case c_name when '' then name else c_name end as name from employee
select case c_name when '' then name else c_name end as name from employee
select case when c_name = '' then name else c_name end as name from employee

name

null

null

name with c_name empty

name

null

null

name with c_name empty

name

null

null

name with c_name empty

select case when c_name != '' then c_name else name end as name from employee
select coalesce(nullif(c_name, ''), name) from employee

name

name with c_name null

name with c_name null 1

name with c_name empty

(No column name)

name with c_name null

name with c_name null 1

name with c_name empty

select isnull(nullif(c_name, ''), name) as name from employee
select nullif (c_name, '') from employee

name

name with

name with

name with

(No column name)

null

null

null

select distinct c_name from employee

c_name

null

c_name	name
null	name with c_name null
null	name with c_name null 1
	name with c_name empty