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;

#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                                             |
+------+-------------------------------------------------+