This is slightly modified from something I found @ http://www.kirupa.com/forum/archive/index.php/t-263260.html Using high-score lists or similar you often have a large number of rows where you want to know who is in 7th place or how well is id:254 doing. This eliminates the slow looping in php of big result-sets by making a sub-query in MySQL. [...]
When you need to switch a fields collation you can check if any existing data will conflict with this change. For example a keyword-field might contain data that is considered unique in one collation but not in another. The Swedish character ä is considered a unique character in swedish collation but in general collation it [...]
Quite simple but something I can never seem to remember: INSERT INTO files_users (file_id, user_id) SELECT id, ’2′ FROM efs.files; found @ http://mysql-tips.blogspot.com/2005/04/mysql-insert-select-example.html
When altering a database, table or field from one character set to another, existing data will probably look garbled since it is expected to be in the new character set. To “convert” existing data is not always easy. This method (found in the comments of a blog entry I have lost the url for) works as long as you can keep the database “locked” when you do this. Otherwise you will convert any new data entered and make that data look garbled.
Altering the character set and collation of a table is sometimes not enough. You may have to alter the actual fields in the table to get MySQL to comply in some cases. I don’t know why or when MySQL does this. ALTER TABLE my_table DEFAULT CHARSET=utf8 COLLATE=utf8_swedish_ci; ALTER TABLE my_table MODIFY my_field varchar(255) CHARACTER [...]
My preferred character set is utf8. One big drawback in many cases can be that the default collation ignores accents for characters. The result is that “halla” and “hallå” is interpreted as the same word. This is of-course bad for storing general data such as names users or products that may very well have accented [...]
This may be useful when for example the character encoding has been messed up and you need to correct existing data. This example will correct swedish accented characters in a uft8 – latin1 mixup. UPDATE my_table SET my_field = REPLACE(my_field,’Ã¥’,'å’); UPDATE my_table SET my_field = REPLACE(my_field,’ä’,'ä’); UPDATE my_table SET my_field = REPLACE(my_field,’ö’,'ö’); [...]