Oracle database merge row records, wmsys WM_ Use of the concat function and group in MySQL_ Use and comparison of concat (ID).

Oracle： wmsys.wm_concat()

Put result set in one column , By comma ‘,’ separate

Columns such as ：

oracle10g The above version provides the function of combining row to column into a string wmsys.wm_concat

　　 For example, there is a users The table is as follows ：

　　id yhm xm

　　1 001 Xiaotang

　　2 002 petty thief

　　3 003 Xiao Zhang

　　selectwmsys.wm_concat(yhm) user name , wmsys.wm_concat(xm) full name from users

　　 The execution result is ：

　　 user name full name

　　001,002,003 Xiaotang , petty thief , Xiao Zhang

 

wmsys.wm_concat() The parameters in can also make multiple , Use ”||” Splicing , The following example ：

select deptno,wmsys.wm_concat(ename || '-' || job) name from emp group by deptno;

The results are shown in the following table ：

deptno	ename
10	CLARK-MANAGER,MILLER-CLERK,KING-PRESIDENT
20	SMITH-CLERK,FORD-ANALYST,ADAMS-CLERK,SCOTT-ANALYST,JONES-MANAGER
30	ALLEN-SALESMAN,JAMES-CLERK,TURNER-SALESMAN,BLAKE-MANAGER,MARTIN-SALESMAN,WARD-SALESMAN

（ You can also use group by Group display and merge ）

MySQL：GROUP_CONCAT()

Put the result set together , Separated by commas by default , You can use [] Set up

With id grouping , hold name The value of the field is printed on one line , Comma separated ( Default )

 

1.  select id,group_concat(name) from aa group by id;  

 

With id grouping , hold name The value of the field is printed on one line , Semicolons separate

1.  select id,group_concat(name separator ';') from aa group 

2.  by id;  

 

With id grouping , Remove redundant name The value of the field is printed on one line ,
Comma separated

Sql Code   

1.  select id,group_concat(distinct name) from aa group by id;