[原創]MySQL數據庫查詢和LVM備份還原學習筆記記錄
一、查詢語句類型:
1)簡單查詢
2)多表查詢
3)子查詢
4)聯合查詢
1)簡單查詢:
SELECT * FROM tb_name;
SELECT field1,field2 FROM tb_name;投影
SELECT [DISTINCT] * FROM tb_name WHERE qualification;選擇
FROM子句:要查詢的關系
表、多個表、其他select語句
WHERE子句:布爾關系表達式
AND,OR,NOT,BETWEEN...AND...,LIKE ‘‘[%:任意長度任意字符;_:任意單個字符],RLIKE,IN,IS NULL,IS NOT NULL
ORDER BY field_name {ASC|DESC}
AS 字段別名
LIMIT [offset,]Count offset偏移量,Count取幾個
聚合:
SUM(),MIN(),MAX(),AVG(),COUNT()
GROUP BY分組:
HAVING:過濾[qualification]
SELECT AVG(Age) FROM students GROUP BY Gender;
ELECT COUNT(CID1) AS Persons,CID1 FROM students GROUP BY CID1;
SELECT COUNT(CID1) AS Persons,CID1 FROM students GROUP BY CID1 HAVING Persons>=2;
SQL語句執行的順序:
start->from->where->group by->having->order by->select fieldN->LIMIT->end
2)多表查詢:
連接:
交叉連接:笛卡爾積
select * from students,courses;
自然連接:內連接,外鏈接:左外連接:... LEFT JOIN ... ON ...,右外連接:... RIGHT JOIN ... ON ...,自連接
select * from students,courses where students.cid1 = courses.cid;
select Name,Cname from students,courses where students.cid1 = courses.cid;
select s.Name,c.Cname from students AS s,courses AS c where s.cid1 = c.cid;
SELECT s.Name,c.Cname FROM students AS s LEFT JOIN courses AS c ON s.CID1=c.CID1;
SELECT s.Name,c.Cname FROM students AS s RIGHT JOIN courses AS c ON s.CID1=c.CID1;
3)子查詢:
比較操作中使用子查詢:子查詢只能返回單個值
IN():使用子查詢
在FROM中使用子查詢
select name from students where Age > (select AVG(Age) from students);
select name from students where Age IN (select Age from tutors);
select Name,Age from (SELECT Name,Age FROM students) AS t where t.Age >= 20;
4)聯合查詢:
UNION:
(select Nmae,Age FROM students) UNION (select Tname,Age from tutors);
二、備份和還原
備份:
select * into OUTFILE ‘/path/beifen.txt‘ from tb_name [where clause];
恢復:
LOAD DATA INFILE ‘/path/beifen.txt‘ INTO TABLE tb_name;
LVM快照備份和還原:
前提:
1、數據文件要在邏輯卷上;
2、此邏輯卷所在卷組必須有足夠空間使用快照卷;
3、數據文件和事務日誌要在同一個邏輯卷上;
步驟:
1、打開會話,施加讀鎖,鎖定所有表:
mysql> FLUSH TABLES WITH READ LOCK;
mysql> FLUSH LOGS;
2、通過另一個終端,保存二進制日誌文件及相關位置信息:
$mysql -uroot -p -e "SHOW MASTER STATUS\G" > /path/master.info
3、創建快照卷:
#lvcreate -L [size] -s -p r -n LV_NAME /path/source_lv
4、釋放鎖:
mysql> UNLOCK TABLES;
5、掛載快照卷,備份:
#mount LV_NAME /mnt -o ro
#cp -a ./* /backup/
#rm -f /backup/mysql-bin.*
6、刪除快照卷:
#lvremove --force LV_NAME
7、增量備份二進制日誌[從master.info文件的位置開始備份,如果還有其他滾動的二進制文件單獨備份即可]:
#mysqlbinlog --start-post=107 mysql-bin.000003 mysql-bin.000004> /backup/incremental.sql
8、還原數據:
#cp -a /bakcup/* /mysql/data/
#service mysqld start
mysql> set sql_log_bin=0;
mysql> source /backup/incremental.sql;
mysql> set sql_log_bin=1;
mysql> SHOW MASTER STATUS\G;
擴展:
MySQL創建表的三種方式:
1)直接手動創建:
mysql> create table tb_name(feild1-N);
2)基於其他表創建新表,這種方式創建的表不會把原表的主鍵,約束,觸發器等復制過來,需要手動在追加。
mysql> create table test_new as select * from test where 1=2; //where 1=2只有表結構沒有數據,where 1=1包括表結構和表數據一起復制了
3)基於原表創建的新表,這種方式使用like關鍵字會將原表的結構都復制過來,包括主鍵,約束,觸發器等。
mysql> create table test like tb_name;
[原創]MySQL數據庫查詢和LVM備份還原學習筆記記錄