translate English to French: If it's very likely that a column has a unique prefix on the first number of characters, it's better to index only this prefix. MySQL supports an index on the leftmost part of a character column.
Dans certaines circonstances, il peut Ãªtre intÃ©ressant de sÃ©parer en deux une table qui est scannÃ©e trÃ¨s souvent.