mysql - mysql中使用concat创建复合索引

Question

使用以下命令我可以获得创建索引命令，

SELECT CONCAT ('
create index ',index_name,' on ',table_schema,'.',table_name,' (',COLUMN_NAME,');'  
) FROM 
inf_schema.STATS WHERE 
table_schema='employee' AND 
table_name='FILESPROC' AND 
index_name NOT LIKE 'PRIMARY' ;

我得到以下输出:

create index FILENAMEPROCID on employee.FILESPROCESSED (PROCID);
create index FILENAMEPROCID on employee.FILESPROCESSED (FILENAME);
create index NENDDATEDataName on employee.FILESPROCESSED (DSN);
create index NENDDATEDataName on employee.FILESPROCESSED (ENDDATE);
create index NENDDATEDataName on employee.FILESPROCESSED (DataName);
create index DSN on employee.FILESPROCESSED (DSN);
create index ENDDATE on employee.FILESPROCESSED (ENDDATE);

但是，我需要以下方式的输出:

create index FILENAMEPROCID on employee.FILESPROCESSED (PROCID, FILENAME);
create index NENDDATEDataName on employee.FILESPROCESSED (DSN, ENDDATE, DataName);
create index DSN on employee.FILESPROCESSED (DSN);
create index ENDDATE on employee.FILESPROCESSED (ENDDATE);

这样我就能够创建复合索引。我该如何实现这一目标？

Answer 1

对具有相同 INDEX_NAME 的所选 COLUMN_NAME 使用 GROUP_CONCAT。

SELECT 
        CONCAT (
          'create index ', index_name, ' on ', table_schema, '.', table_name, 
          ' ( ', GROUP_CONCAT( COLUMN_NAME SEPARATOR ', ' ), ' );'  
        ) indexes_scripts
  FROM 
        inf_schema.STATS 
 WHERE 
        table_schema='employee' 
   AND  table_name='FILESPROC'
   AND  index_name NOT LIKE 'PRIMARY' 
 GROUP BY index_name