You may come across the following error when you try to import the customizations for an entity that already exists in the system.
This error is often a result of data type mismatch between the attributes in the new customization file being imported and the entity attributes already defined in CRM. Say for example an entity has an attirbute of the type picklist in CRM. However the same attribute is now defined to be of the data type int in the new customization file that needs to be imported. CRM allows for onyl unique attribute names. Now since it already has an attribute of the same name but a different data type it cannot overwrite that attribute with the new data type defined in the customization file.
To fix the problem, you need to delete the existing attribute from CRM entity. Publish the entity customizations. Now try to re-import the customization file. It will import without any SQL errors.