Learning Mysql
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| Exercises 1. Write the monitor command to import the file academics.tsv, which has its values separated by tabs, into the details table. Hint the tab character is shown with the \t escape sequence. When would you need to insert data using a query. What’s the difference between REPLACE and INSERT IGNORE ? Exercises | 295 4. What can you tell from this output produced by the EXPLAIN command? +----+-------------+------------+-------+---------------+---------+... | id | select_type | table | type | possible_keys | key |... +----+-------------+------------+-------+---------------+---------+... | 1 | SIMPLE | supervisor | const | PRIMARY | PRIMARY |... | 1 | SIMPLE | student | ALL | NULL | NULL |... | 1 | SIMPLE | supervises | index | NULL | PRIMARY |... +----+-------------+------------+-------+---------------+---------+... ... +---------+-------+------+------------------------------------+ ... | key_len | ref | rows | Extra | ... +---------+-------+------+------------------------------------+ ... | 4 | const | 1 | Using index Using temporary | ... | NULL | NULL | 95 | | ... | 12 | NULL | 570 | Using where Using index Distinct | ... +---------+-------+------+------------------------------------+ 3 rows inset sec. What can you tell from this output produced by the EXPLAIN command? +-----+--------------+------------+--------+---------------+---------+---------+... | id | select_type | table | type | possible_keys | key | key_len |... +-----+--------------+------------+--------+---------------+---------+---------+... | 1 | PRIMARY | played | index | PRIMARY | PRIMARY | 10 |... | 1 | PRIMARY | track | eq_ref | PRIMARY | PRIMARY | 6 |... | 2 | UNION | played | index | PRIMARY | PRIMARY | 10 |... | 2 | UNION | track | eq_ref | PRIMARY | PRIMARY | 6 |... | NULL UNION RESULT | +-----+--------------+------------+--------+---------------+---------+---------+... ...+--------------------------------------------------------------------+------+... ...| ref | rows |... ...+--------------------------------------------------------------------+------+... ...| | 12 |... ...| music.played.artist_id,music.played.album_id,music.played.track_id | 1 |... ...| | 12 |... ...| music.played.artist_id,music.played.album_id,music.played.track_id | 1 |... ...| | NULL |... ...+--------------------------------------------------------------------+------+... ...+-----------------------------+ ...| Extra | ...+-----------------------------+ ...| Using index Using filesort | ...| | ...| Using index Using filesort | ...| | ...| | ...+-----------------------------+ 5 rows inset sec) Download 4.24 Mb. Share with your friends:
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