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Luca Vicini
Courses Plus Student 8,594 PointsVARCHAR(xxx) memory space allocation
mysql CREATE TABLE movies (title VARCHAR(200), year INTEGER);
Does it means that each row in the database is going to occupy 204 bytes (200 bytes for the movie title plus 4 bytes for the integer), no matter the data in it?
2 Answers
Hugo Paz
15,622 PointsNo. The size will depend of what is stored there. The only issue might be possible performance impact: in MySQL, temporary tables and MEMORY tables store a VARCHAR column as a fixed-length column, padded out to its maximum length. If you design VARCHAR columns much larger than the greatest size you need, you will consume more memory than you have to. This affects cache efficiency, sorting speed, etc.
Luca Vicini
Courses Plus Student 8,594 PointsHi Hugo, Great thanks for your answer. I read in the MySql documentation that temporary tables are created and dropped during the same session and MEMORY tables live only in RAM. Does this mean that when a MySQL server works with the tables, it stores VARCHAR as a fixed length column in RAM, but optimise the size when storing to hard disk? Cheers Luca
Matthew Day
6,740 PointsGreat question. I, too, would like to know the answer to this one.