Mysql储存过程7: case

#用在储存过程中:
 
create procedure k()
  begin
  declare number int;
  set number = floor(rand(0)*2);
  case number
    when number > 0 then
      select '>0';
    else
      select '=0';
  end case;
  end$
 
#用在查询中:
select case user when 'root' then 'yes' else 'no' end from mysql.user;
select case  when user='root' then 'yes' else 'no' end from mysql.user;

注意这个case用在储存过程中与用在查询语句中是不一样的。

储存过程中要用end case结束， 用在一般查询中是end结束。

#储存过程case语法
case value
  when 条件 then
  SQL
  [when 条件 then]
  SQL
  [else]
  SQL
  end case;
 
#用在搜索中的case语法:
1.case when column=value then 'output1' else 'output2' end from database.table;
2.case column when 'value' then 'output1' else 'output2' end from database.table;
 
select case when column=value then 'output1' else 'output2' end  from database.table;
 
mysql> select user,case  when user='root' then 'yes' else 'no' end from mysql.user;$
+------+-------------------------------------------------+
| user | case  when user='root' then 'yes' else 'no' end |
+------+-------------------------------------------------+
| root | yes                                             |
| root | yes                                             |
| root | yes                                             |
+------+-------------------------------------------------+

用法可参以参考一下这里:

http://www.cnblogs.com/perl6/p/6995593.html