Mysql筆記

#導入數據庫 [1]
一、首先建空數據庫
mysql > create database abc;

二、導入數據庫
方法一：
（1）選擇數據庫
    mysql > use abc;
（2）設置數據庫編碼
    mysql > set names utf8;
（3）導入數據（注意sql文件的路徑）
    mysql > source /home/abc/abc.sql;
方法二：
    mysql -u用戶名 -p密碼 數據庫名 < 數據庫名.sql
    #mysql -uabc_f -p abc < abc.sql

建議使用第二種方法導入。
注意：有命令行模式，有sql命令

#根據積分查詢用戶排名 [1]
select * from (
  SELECT @rownum:=@rownum+1 as rownum, id, nickname FROM `wx_user`, (select @rownum:=0) t order by user_score desc
) as a where a.id = 2

#修改自增ID
ALTER TABLE wx_user_test auto_increment = 40 ;

#查看鏈接
show processlist;
kill  id

#Mysql 獲取一小時前時間
select date_sub(now(), interval 1 hour);
select date_sub(now(), interval -1 hour);　　　　　　//一小時後
select date_add(now(), interval 1 hour);　　　　　　 //一小時後, 更多可選值參考[1] [2]

#日期時間轉時間戳 [1]
SELECT UNIX_TIMESTAMP( DATE_ADD( NOW( ) , INTERVAL -3 DAY ) ) ;

#時間戳轉時期時間
SELECT *, FROM_UNIXTIME( created_at, '%Y-%m-%d %H:%i:%s' ) as date1 FROM `user`;

#查看數據庫中全部表的記錄數 [1]
select table_name,table_rows from information_schema.tables 
where TABLE_SCHEMA = 'test'   
order by table_name desc;

#建立一個和已經存在表結構相同的表
CREATE TABLE wx_user1 LIKE wx_user;

#重命名錶
RENAME TABLE  `wx_user1` TO  `wx_user` ;

#查看索引
SHOW INDEX FROM wx_user;

#添加多字段惟一索引
ALTER TABLE  `book` ADD UNIQUE (`book_id`,`page_num`)

#刪除索引 [1]
ALTER TABLE wx_user DROP INDEX openid_2;

#新建數據庫
CREATE DATABASE  `test2` DEFAULT CHARACTER SET utf8    COLLATE utf8_general_ci;
CREATE DATABASE  `test2` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci;

#查看數據庫編碼
SHOW VARIABLES LIKE '%character%'

#查詢數據庫中指定表的全部字段名 [1]
SELECT GROUP_CONCAT( COLUMN_NAME SEPARATOR ", " ) FROM information_schema.COLUMNS WHERE table_name = 'wx_user' AND table_schema = "database_name"

#用select的數據更新另外一個表中數據 [1]
UPDATE wx_user AS a INNER JOIN (
	SELECT uid, COUNT( 1 ) AS read_count_total
	FROM wx_book_read
	WHERE status = 1
	GROUP BY uid
) AS b ON a.id = b.uid
SET a.read_count = b.read_count_total

UPDATE wx_book_read_page AS a 
LEFT JOIN wx_book_read AS b 
ON  a.book_id = b.book_id 
AND a.uid = b.uid 
SET a.book_read_id = b.id

#查看mysql配置文件在哪
/usr/sbin/mysqld --verbose --help|grep -A 1 'Default options'

#替換mysql字段中部份內容
UPDATE wx_user SET image = REPLACE(image , 'http://', 'https://') WHERE id = 1;

#mysql字符串拼接
UPDATE  `goods_cat` SET name = CONCAT( name,  '2' ) WHERE TYPE =2;

#mysql字符串處理函數
LENGTH(TRIM(url)), LENGTH(url)
CHAR_LENGTH

#mysql按in中內容排序 [1]
SELECT id, title, description, 
TYPE FROM wx_article
WHERE id
IN ( 784, 743, 596, 659, 685, 617, 836, 815, 813, 774 ) 
ORDER BY INSTR(  ',784,743,596,659,685,617,836,815,813,774,', CONCAT(  ',', id,  ',' ) ) 

SELECT id, title, description,  FIELD( id, 3, 5, 1, 4, 2 ) as order_data
FROM wx_article
WHERE ID
IN ( 3, 5, 1, 4, 2 ) 
ORDER BY FIELD( id, 3, 5, 1, 4, 2 ) 

SELECT FIELD( 1, 3, 5, 1, 4, 2 );//3

#隨機閱讀次數100-200次
select @i:=100;select @j:=200;
UPDATE `wx_article_test` SET `view_count` = FLOOR(@i + rand() * (@j - @i + 1)) WHERE 1;