【问题】

I am new to jasper. I am having a problem to design a report which does the same like group_concat() function in my sql..  i am using a sql server so cannot use that function in my query.

My input is something like this.

Col1   Col2    Col3     Col4
10       1234    Sam     A12G3
10       1234    Sam     K78DE
10       1234    Sam     MAT12
20      1456    Tom     E12F4
20      1456    Tom     KAR3R
20      3217    Tom      G45G4

my output should be like 

Col1   Col2    Col3     Col4
10       1234    Sam     A12G3 , K78DE , MAT12  
20      1456    Tom     E12F4 , KAR3R
20      3217    Tom      G45G4

I am trying to create a variable using the below expression.

Class : java.lang.String ,  CALCULATION: Nothing , Incrementype: Group , Incrementgroup: Col2

expression is  $F{Col4} + "," + $F{Col4}

this one is not working.. Could you please help me on this please

【回答】

SQL 和 Jasper 应该都能实现 group_concat 函数，只是代码比较难写。可以试试用 SPL 来辅助 Jasper。

如下代码就能实现与 group_concat 等价的功能，而且与数据库无关：

	A
1	=mySqlDB.query("select * from   table1"). group(Col1,Col2,Col3;~.(Col4).concat@c():Col4)

集算器提供 JDBC 接口与 Jasper 集成，与数据库的用法相同，详情参考【JasperReport 调用 SPL 脚本】