# mysql 存取
* 搜尋某欄位所有的唯一值
`SELECT DISTINCT mycolumn FROM mytable`

* 總計(sum、count、average)搜尋結果
`SELECT SUM(mycolumn) FROM mytable`

* 秀出所有欄位資訊
`SHOW COLUMNS FROM my_table;`

* 搜尋特定時間欄位
`SELECT *
FROM events
WHERE event_date BETWEEN date_sub(now(), interval 1 week) AND date_add(now(), interval 3 day);`
https://popsql.com/learn-sql/mysql/how-to-query-date-and-time-in-mysql/
* 複製db
* `mysqldump -u root -p source_db > d:\db\source_db.sql`
* `mysql -u root -p destination_db < d:\db\source_db.sql`
* 連線數量查詢(default 100)
`mysql> show variables like 'max_connections';`

* For formatted output:

describe [db_name.]table_name;
* For an SQL statement that can be used to create a table:

show create table [db_name.]table_name;

###### tags: `linux` `mysql`