Question

I am copying the schema of an empty table in a newer version of ISPConfig into the database of an older version. In the newer version, there are two keys and a primary key. Here’s the second key, missing from the table with data. As you can see it says “MUL” indicating it is a non-unique key:

*************************** 10. row ***************************  
  Field: type  
   Type: enum('alias','aliasdomain','forward','catchall')  
   Null: NO  
    Key: MUL  
Default: alias  
  Extra:  

On the other table, with data, MUL is missing:

*************************** 10. row ***************************  
  Field: type  
   Type: enum('alias','aliasdomain','forward','catchall')  
   Null: NO  
    Key:  
Default: alias  
  Extra:  

Is there any way I can add “MUL” to the ‘type’ column without data loss?

Answer 1

Use SHOW CREATE TABLE tablename to see all the indexes in each table. Then use ALTER TABLE oldtable ADD INDEX ... to add the missing indexes to the old table.