sql,SELECT table_schema, ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS "Size (MB)" FROM information_schema.tables GROUP BY table_schema;,
``sql,SELECT table_schema, ROUND(SUM(data_length + index_length) / 1024 / 1024, 2) AS "Size (MB)" FROM information_schema.tables GROUP BY table_schema;,
``ORDER BY RAND()
来实现随机查询。,,``sql,SELECT * FROM your_table ORDER BY RAND() LIMIT 10;,
`,,这条语句会从
your_table` 表中随机选择 10 条记录。DATE()
, TIME()
, NOW()
等函数来查询和操作时间。,,``sql,SELECT NOW(); 获取当前日期和时间,SELECT DATE(NOW()); 获取当前日期,SELECT TIME(NOW()); 获取当前时间,
``DATE_SUB
函数结合 NOW()
函数来按时间间隔查询数据。要查询过去7天内的数据,可以使用以下SQL语句:,,``sql,SELECT * FROM your_table WHERE your_date_column >= DATE_SUB(NOW(), INTERVAL 7 DAY);,
``MATCH()...AGAINST()
语法,适用于大文本的高效搜索。AS
关键字给表取别名,SELECT * FROM table_name AS alias;
。sql,SELECT a.*, b.*,FROM table1 a,JOIN table2 b ON a.id = b.a_id;,
``,,这条语句将table1和table2通过a.id和b.a_id进行关联查询。Powered By Z-BlogPHP 1.7.3
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