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This thread is resolved. Here is a description of the problem and solution.

Problem: Solve the database error found in WPML -> Translation Management. The error message is: [Illegal mix of collations for operation 'UNION']

Solution: In the database, make sure that all table are using the same collation, for example ex.utf8mb4_unicode_ci.

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This topic contains 2 replies, has 2 voices.

Last updated by patrizio-romanoD 4 years, 8 months ago.

Assigned support staff: Bobby.

Author Posts
September 14, 2016 at 8:55 am #1078966


I am trying to:
Solve the database error fond in WPML -> Translation Management
The message: [Illegal mix of collations for operation 'UNION'] ...

I tried to follow the step described above this solved thread here:

BUT I can't get what to do, as:

The screenshots in that thread show all _ICL_ prefix tables with utf8mb4_unicode_ci collation while, all _ICL_ prefix tables in my installations show utf8mb4_unicode_520_ci collation;

The bunch of tables the support guy suggests to change show utf8_general_ci collation
while I have utf8mb4_unicode_ci in many, utf8_general_ci in others, and I cannot get, from this and other similar thread, which tables' collation should I change and how.

Which tables exactly should I alter, and how?
Should I make other tables collations match the same as the _ICL_ one?
Or should I try the other way, changing the _ICL_ prefix tables to match the other collation?

Sorry for the apparent mess, I'm really puzzled as I'm trying to get a big installation with a lot of tables work fine with translations, so please be patient 🙂

September 14, 2016 at 12:05 pm #1079460


Languages: English (English )

Timezone: America/Los_Angeles (GMT-07:00)


Thank you for contacting WPML Support,

I understand that this issue and its solution sometimes can be a bit confusing !

You will need to pick one collation and the tables that have been pointed out to you will need to all have the same one

just pick one and make sure that they all are the same within those table

I hope this helps to clear things out a bit if you are still having trouble please let me know and i can take a closer look

Kind Regards,

September 19, 2016 at 6:48 am #1086728


Sorry for not replying sooner,
I made a new installation of WPML from scratch and that solved my issue, apparently no database errors anymore.