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- mysql,如何在排序之后的数据中读取其中某些条数据
A1 A2 A3
1 2 工资
结果是什么
比如:
A1 A2 A3
1 2 工资
结果是什么
...着实不懂。我就是想写个存储过程,通过表A的定义将总表B里面的有用信息筛选出来填到一个新表C中...您问的结果是什么具体指?懂的有限,还望不吝赐教。谢谢!
A1 A2 A3
1 2 工资
select 工资 from b ?
mysql> select * from config;
+----+----------+
| id | name |
+----+----------+
| 1 | salary |
| 2 | bonus |
| 3 | overtime |
+----+----------+
3 rows in set (0.00 sec)mysql> select * from data;
+--------+-------+----------+
| salary | bonus | overtime |
+--------+-------+----------+
| 1 | 2 | 4 |
| 3 | 3 | 3 |
+--------+-------+----------+
2 rows in set (0.00 sec)mysql> select @sql := concat("select ", group_concat(name), " from data;")
-> from config
-> where id in (1, 2);
+--------------------------------------------------------------+
| @sql := concat("select ", group_concat(name), " from data;") |
+--------------------------------------------------------------+
| select salary,bonus from data; |
+--------------------------------------------------------------+
1 row in set (0.00 sec)mysql>
mysql> prepare sp from @sql;
Query OK, 0 rows affected (0.00 sec)
Statement preparedmysql> execute sp;
+--------+-------+
| salary | bonus |
+--------+-------+
| 1 | 2 |
| 3 | 3 |
+--------+-------+
2 rows in set (0.00 sec)mysql> drop prepare sp;
Query OK, 0 rows affected (0.00 sec)
MySQL交叉表
在某些数据库中有交叉表,但在MySQL中却没有这个功能,但网上看到有不少朋友想找出一个解决方法,特发贴集思广义。http://topic.csdn.net/u/20090530/23/0b782674-4b0b-4cf5-bc1a-e8914aaee5ab.html?96198现整理解法如下:数据样本: create table tx( id int primary key, c1 c...
declare Ttype varchar(30);declare Tid int;declare Tmin int;declare Tmax int;select min(A1) into Tmin from A;select max(A1) into Tmax from A;while Tmin<=Tmax do select A3 into Ttype from A where A1=Tmin;-- C表C2字段 类型名 select A1 into Tid from A where A3=Tmin;-- C表C1字段 类型定义ID(来源A表) set @Tsql=concat("insert into C(C1,C2) select ",Tid,",",Ttype," from B;"); prepare Ttidy from @Tsql; execute Tidy; -- C表插入数据;Tmin=Tmin+1;end while;