notes.txt

+ for writing playground codes: write them in test moudle and then call it form an excutable file > but b/c
    rust compiler ignores test moudles when you play comment the "#[cfg(test)]" section.

+ About rust:
    + Empty String and Vec have zero capacity means they do not allocate unless something goes inot them.

+ MySQL Notes:
    + for copying a table: CREATE TABLE blogs2 LIKE blogs;
    + copy tables: INSERT INTO blogs2 (SELECT * FROM `blogs`); // https://www.mysqltutorial.org/mysql-copy-table-data.aspx
    + CREATE TABLE sms_bk SELECT * FROM sms [[where]];
    + SHOW CREATE TABLE `blogs`;
    + ALTER TABLE table_name ENGINE engine_name;
    + SHOW ENGINES;
    + SHOW CREATE DATABASE twitter;
    + DELETE FROM blogs; // dangerous
    + mysqldump -u flipper -p --all-databases >bk1.sql
    + RENAME TABLE t TO t_old, t_copy TO t;

+ Others
    + hexdump -C ./all.sh