weibanggang
create table test(
id int primary key auto_increment,
name varchar(20),
sex int 
)
insert into test(name,sex) values(\'小明\',1),(\'小兰\',0),(\'小邹\',1),(\'小孟\',0)

select id ,name ,if(sex=1,\'\',\'\') from test

select id ,name ,case sex when 1 then \'\' else \'\' end as sex from test

  if([字段名]=[条件],[为真时返回],[为假时返回])

  case [字段名] when [条件] then [为真时返回] else [为假时返回] end as sex from test

   case [字段名] when [条件] then [为真时返回]  end as sex from test  (该语句为假时候返回null)

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