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1.显示数据库mysql> show databases;+--------------------+| Database |+--------------------+| information_schema || mysql |+--------------------+2 rows in set (0.00 sec)2.选择一个数据库mysql> use mysqlReading table information for completion of table and column namesYou can turn off this feature to get a qu 阅读全文
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mysql -h localhost -u root -p 阅读全文
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irb(main):005:0> [1,1,3,5] & [1,2,3]=> [1, 3]irb(main):006:0> [1,2,3] * 3=> [1, 2, 3, 1, 2, 3, 1, 2, 3]irb(main):007:0> [1,2,3 ] * "--"=> "1--2--3"irb(main):008:0> [1,1,2,2,3,3,4,5]-[1,2,4]=> [3, 3, 5]irb(main):009:0> [1,2] <<'c'<&l 阅读全文