在MySQL存儲過程的語句中有三個標準的循環方式：WHILE循環，LOOP循環以及REPEAT循環。還有一種非標準的循環方式：GOTO，不過這種循環方式最好別用，很容易引起程序的混亂，在這里就不錯具體介紹了。

這幾個循環語句的格式如下：
WHILE……DO……END WHILE
REPEAT……UNTIL END REPEAT
LOOP……END LOOP
GOTO。

    下面首先使用第一種循環編寫一個例子。
mysql> create procedure pro10()
    -> begin
    -> declare i int;
    -> set i=0;
    -> while i<5 do
    ->     insert into t1(filed) values(i);
    ->     set i=i+1;
    -> end while;
    -> end;//
Query OK, 0 rows affected (0.00 sec)
    在這個例子中，INSERT和SET語句在WHILE和END WHILE之間，當變量i大于等于5的時候就退出循環。使用set i=0；語句是為了防止一個常見的錯誤，如果沒有初始化，i默認變量值為NULL，而NULL和任何值操作的結果都是NULL。
    執行一下這個存儲過程并產看一下執行結果：
mysql> delete from t1//
Query OK, 0 rows affected (0.00 sec)
mysql> call pro10()//
Query OK, 1 row affected (0.00 sec)
mysql> select * from t1//
+——-+
| filed |
+——-+
|     0 |
|     1 |
|     2 |
|     3 |
|     4 |
+——-+
5 rows in set (0.00 sec)
    以上就是執行結果，有5行數據插入到數據庫中，證明存儲過程編寫正確無誤^_^。

    再來看一下第二個循環控制指令 REPEAT……END REPEAT。使用REPEAT循環控制語句編寫下面這個存儲過程：
mysql> create procedure pro11()
    -> begin
    -> declare i int default 0;
    -> repeat
    ->     insert into t1(filed) values(i);
    ->     set i=i+1;
    ->     until i>=5
    -> end repeat;
    -> end;//
Query OK, 0 rows affected (0.00 sec)
    這個REPEAT循環的功能和前面WHILE循環一樣，區別在于它的執行后檢查是否滿足循環條件（until i>=5），而WHILE則是執行前檢查（while i<5 do）。
    不過要注意until i>=5后面不要加分號，如果加分號，就是提示語法錯誤。
    編寫完成后，調用一下這個存儲過程，并查看結果：
mysql> delete from t1//
Query OK, 5 rows affected (0.00 sec)

mysql> call pro11()//
Query OK, 1 row affected (0.00 sec) #雖然在這里顯示只有一行數據受到影響，但是下面選擇數據的話，還是插入了5行數據。

mysql> select * from t1//
+——-+
| filed |
+——-+
|     0 |
|     1 |
|     2 |
|     3 |
|     4 |
+——-+
5 rows in set (0.00 sec)
一行就是執行結果，實際的作用和使用while編寫的存儲過程一樣，都是插入5行數據。

一、配置文件的修改
    1.#sudo vim /etc/mysql/my.cnf

    找到 bind-address = 127.0.0.1
    注釋掉這句話
 
二、Mysql數據庫的修改
1) [root@etc etc]# mysql -u  root  -p
Enter password:
2)mysql> use mysql;
3)mysql> select host,user,password from user;
4)grant all privileges on *.* to  root@192.168.15.101  identified by 'password'
 注意： （1）192.168.15.101是欲連接到此Mysql數據庫的客戶端的IP地址，而不是Mysql數據庫所在數據庫服務器的IP地址，切記。這里也可以使用'%'代替所有ip
              （2）password就是Mysql數據庫root用戶的password,根據實際情況需要修改

三、再次用Mysql客戶端登陸

本文來自CSDN博客，轉載請標明出處：http://blog.csdn.net/bjblues/archive/2008/02/04/2083934.aspx

select id, username from user where id>1
INTERSECT
select id, username from user where id<3

can simply be rewritten to

select id, username from user inner join
(select id, username from user where id <3) as b using (id, username)
where id>1

Java代碼

1. CREATE TABLE Movie(   
2. id           INT NOT NULL AUTO_INCREMENT,   
3. name     VARCHAR(60) NOT NULL,   
4. released YEAR NOT NULL,   
5. PRIMARY KEY (id)   
6. ) ENGINE=InnoDB;  

CREATE TABLE Movie(
id           INT NOT NULL AUTO_INCREMENT,
name     VARCHAR(60) NOT NULL,
released YEAR NOT NULL,
PRIMARY KEY (id)
) ENGINE=InnoDB;

Java代碼

1. INSERT INTO Movie (name,released) VALUES ('Gladiator',2000);   
2. INSERT INTO Movie (id,name,released) VALUES (NULL,'The Bourne Identity',1998);  

INSERT INTO Movie (name,released) VALUES ('Gladiator',2000);
INSERT INTO Movie (id,name,released) VALUES (NULL,'The Bourne Identity',1998);

Java代碼

1. CREATE TABLE Movie(   
2. id          INT NOT NULL,   
3. name     VARCHAR2(60) NOT NULL,   
4. released INT NOT NULL,   
5. PRIMARY KEY (id)   
6. );   
7. CREATE SEQUENCE MovieSeq;  

CREATE TABLE Movie(
id          INT NOT NULL,
name     VARCHAR2(60) NOT NULL,
released INT NOT NULL,
PRIMARY KEY (id)
);
CREATE SEQUENCE MovieSeq;

Java代碼

1. INSERT INTO Movie (id,name,released) VALUES (MovieSeq.NEXTVAL,'Gladiator',2000);  

INSERT INTO Movie (id,name,released) VALUES (MovieSeq.NEXTVAL,'Gladiator',2000);

Java代碼

1. CREATE OR REPLACE TRIGGER BRI_MOVIE_TRG   
2. BEFORE INSERT ON Movie   
3. FOR EACH ROW   
4. BEGIN   
5.   SELECT MovieSeq.NEXTVAL INTO :new.id FROM DUAL;   
6. END BRI_MOVIE_TRG;   
7. .   
8. RUN;  

CREATE OR REPLACE TRIGGER BRI_MOVIE_TRG
BEFORE INSERT ON Movie
FOR EACH ROW
BEGIN
SELECT MovieSeq.NEXTVAL INTO :new.id FROM DUAL;
END BRI_MOVIE_TRG;
.
RUN;

Java代碼

1. INSERT INTO Movie (name,released) VALUES ('The Lion King',1994);  

INSERT INTO Movie (name,released) VALUES ('The Lion King',1994);

NEXTVAL(’sequence’);
CURRVAL(’sequence’);
SETVAL(’sequence’,value);

Java代碼

1. DROP TABLE IF EXISTS sequence;   
2. CREATE TABLE sequence (   
3. name              VARCHAR(50) NOT NULL,   
4. current_value INT NOT NULL,   
5. increment       INT NOT NULL DEFAULT 1,   
6. PRIMARY KEY (name)   
7. ) ENGINE=InnoDB;   
8. INSERT INTO sequence VALUES ('MovieSeq',3,5);   
9. DROP FUNCTION IF EXISTS currval;   
10. DELIMITER $   
11. CREATE FUNCTION currval (seq_name VARCHAR(50))   
12. RETURNS INTEGER   
13. CONTAINS SQL   
14. BEGIN   
15.   DECLARE value INTEGER;   
16.   SET value = 0;   
17.   SELECT current_value INTO value   
18.   FROM sequence   
19.   WHERE name = seq_name;   
20.   RETURN value;   
21. END$   
22. DELIMITER ;  

DROP TABLE IF EXISTS sequence;
CREATE TABLE sequence (
name              VARCHAR(50) NOT NULL,
current_value INT NOT NULL,
increment       INT NOT NULL DEFAULT 1,
PRIMARY KEY (name)
) ENGINE=InnoDB;
INSERT INTO sequence VALUES ('MovieSeq',3,5);
DROP FUNCTION IF EXISTS currval;
DELIMITER $
CREATE FUNCTION currval (seq_name VARCHAR(50))
RETURNS INTEGER
CONTAINS SQL
BEGIN
DECLARE value INTEGER;
SET value = 0;
SELECT current_value INTO value
FROM sequence
WHERE name = seq_name;
RETURN value;
END$
DELIMITER ;

Java代碼

1. mysql> SELECT currval('MovieSeq');   
2. +---------------------+   
3. | currval('MovieSeq') |   
4. +---------------------+   
5. |                   3 |   
6. +---------------------+   
7. 1 row in set (0.00 sec)   
8. mysql> SELECT currval('x');   
9. +--------------+   
10. | currval('x') |   
11. +--------------+   
12. |            0 |   
13. +--------------+   
14. 1 row in set, 1 warning (0.00 sec)   
15. mysql> show warnings;   
16. +---------+------+------------------+   
17. | Level   | Code | Message          |   
18. +---------+------+------------------+   
19. | Warning | 1329 | No data to FETCH |   
20. +---------+------+------------------+   
21. 1 row in set (0.00 sec)  

mysql> SELECT currval('MovieSeq');
+---------------------+
| currval('MovieSeq') |
+---------------------+
|                   3 |
+---------------------+
1 row in set (0.00 sec)
mysql> SELECT currval('x');
+--------------+
| currval('x') |
+--------------+
|            0 |
+--------------+
1 row in set, 1 warning (0.00 sec)
mysql> show warnings;
+---------+------+------------------+
| Level   | Code | Message          |
+---------+------+------------------+
| Warning | 1329 | No data to FETCH |
+---------+------+------------------+
1 row in set (0.00 sec)

Java代碼

1. DROP FUNCTION IF EXISTS nextval;   
2. DELIMITER $   
3. CREATE FUNCTION nextval (seq_name VARCHAR(50))   
4. RETURNS INTEGER   
5. CONTAINS SQL   
6. BEGIN   
7.    UPDATE sequence   
8.    SET          current_value = current_value + increment   
9.    WHERE name = seq_name;   
10.    RETURN currval(seq_name);   
11. END$   
12. DELIMITER ;  

DROP FUNCTION IF EXISTS nextval;
DELIMITER $
CREATE FUNCTION nextval (seq_name VARCHAR(50))
RETURNS INTEGER
CONTAINS SQL
BEGIN
UPDATE sequence
SET          current_value = current_value + increment
WHERE name = seq_name;
RETURN currval(seq_name);
END$
DELIMITER ;

Java代碼

1. mysql> select nextval('MovieSeq');   
2. +---------------------+   
3. | nextval('MovieSeq') |   
4. +---------------------+   
5. |                  15 |   
6. +---------------------+   
7. 1 row in set (0.09 sec)   
8.   
9. mysql> select nextval('MovieSeq');   
10. +---------------------+   
11. | nextval('MovieSeq') |   
12. +---------------------+   
13. |                  20 |   
14. +---------------------+   
15. 1 row in set (0.01 sec)   
16.   
17. mysql> select nextval('MovieSeq');   
18. +---------------------+   
19. | nextval('MovieSeq') |   
20. +---------------------+   
21. |                  25 |   
22. +---------------------+   
23. 1 row in set (0.00 sec)  

mysql> select nextval('MovieSeq');
+---------------------+
| nextval('MovieSeq') |
+---------------------+
|                  15 |
+---------------------+
1 row in set (0.09 sec)
mysql> select nextval('MovieSeq');
+---------------------+
| nextval('MovieSeq') |
+---------------------+
|                  20 |
+---------------------+
1 row in set (0.01 sec)
mysql> select nextval('MovieSeq');
+---------------------+
| nextval('MovieSeq') |
+---------------------+
|                  25 |
+---------------------+
1 row in set (0.00 sec)

Java代碼

1. DROP FUNCTION IF EXISTS setval;   
2. DELIMITER $   
3. CREATE FUNCTION setval (seq_name VARCHAR(50), value INTEGER)   
4. RETURNS INTEGER   
5. CONTAINS SQL   
6. BEGIN   
7.    UPDATE sequence   
8.    SET          current_value = value   
9.    WHERE name = seq_name;   
10.    RETURN currval(seq_name);   
11. END$   
12. DELIMITER ;  

DROP FUNCTION IF EXISTS setval;
DELIMITER $
CREATE FUNCTION setval (seq_name VARCHAR(50), value INTEGER)
RETURNS INTEGER
CONTAINS SQL
BEGIN
UPDATE sequence
SET          current_value = value
WHERE name = seq_name;
RETURN currval(seq_name);
END$
DELIMITER ;

Java代碼

1. mysql> select setval('MovieSeq',150);   
2. +------------------------+   
3. | setval('MovieSeq',150) |   
4. +------------------------+   
5. |                    150 |   
6. +------------------------+   
7. 1 row in set (0.06 sec)   
8.   
9. mysql> select curval('MovieSeq');   
10. +---------------------+   
11. | currval('MovieSeq') |   
12. +---------------------+   
13. |                 150 |   
14. +---------------------+   
15. 1 row in set (0.00 sec)   
16.   
17. mysql> select nextval('MovieSeq');   
18. +---------------------+   
19. | nextval('MovieSeq') |   
20. +---------------------+   
21. |                 155 |   
22. +---------------------+   
23. 1 row in set (0.00 sec)  

package com.founder.demo;

import Java.sql.Connection;
import Java.sql.DriverManager;
import Java.sql.PreparedStatement;
import Java.sql.ResultSet;
import Java.sql.Statement;

public class ImportCSV {

 public static void main(String[] args) {
  try {
   // load the driver into memory
   Class.forName("org.relique.jdbc.csv.CsvDriver");

   // create a connection. The first command line parameter is assumed to
   //  be the directory in which the .csv files are held
   Connection conn = DriverManager
     .getConnection("jdbc:relique:csv:H:\\PythonWorkSpace");

   // create a Statement object to execute the query with
   Statement stmt = conn.createStatement();

   // Select the columns from csv file
   ResultSet results = stmt
     .executeQuery("SELECT ORDER_NO,ARTICLE_NO,CATALOG_NO,DESCRIPTION,QUANTITY,ISO_UNIT,UNIT,MDL_NO,CAS, "
       + " MOLECULA,FORMULA,DENSITY,PRICE_EUR,UN_NO,DANGER_GR,DANGER_CLASS,ZUSATZGEFAHR1,ZUSATZGEFAHR2,R_PHRASES, "
       + " S_PHRASES,DANGER_SYMBOL,STORAGE_TEMPERATURE FROM ABCR");
   
   //MySQL
   Class.forName("com.mysql.jdbc.Driver").newInstance();
   Connection con = Java.sql.DriverManager
     .getConnection(
       "jdbc:mysql://localhost/chemicaldb?useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull",
       "root", "root");

   String sql = "INSERT INTO meryer_abcr (ORDER_NO,ARTICLE_NO,CATALOG_NO,DESCRIPTION,QUANTITY,ISO_UNIT,UNIT,MDL_NO,CAS, "
     + " MOLECULA_FORMULA,MOLECULAR_WEIGHT,DENSITY,PRICE_EUR,UN_NO,DANGER_GROUP,DANGER_CLASS,ZUSATZGEFAHR1,ZUSATZGEFAHR2,R_PHRASES, "
     + " S_PHRASES,DANGER_SYMBOL,STORAGE_TEMPERATURE) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";

   PreparedStatement mstmt = con.prepareStatement(sql);

   // dump out the results and set params
   while (results.next()) {
    mstmt.setString(1, results.getString("ORDER_NO"));
    mstmt.setString(2, results.getString("ARTICLE_NO"));
    mstmt.setString(3, results.getString("CATALOG_NO"));
    mstmt.setString(4, results.getString("DESCRIPTION"));
    mstmt.setString(5, results.getString("QUANTITY"));
    mstmt.setString(6, results.getString("ISO_UNIT"));
    mstmt.setString(7, results.getString("UNIT"));
    mstmt.setString(8, results.getString("MDL_NO"));
    mstmt.setString(9, results.getString("CAS"));
    mstmt.setString(10, results.getString("MOLECULA_FORMULA"));
    mstmt.setString(11, results.getString("MOLECULAR_WEIGHT"));
    mstmt.setString(12, results.getString("DENSITY"));
    mstmt.setString(13, results.getString("PRICE_EUR"));
    mstmt.setString(14, results.getString("UN_NO"));
    mstmt.setString(15, results.getString("DANGER_GROUP"));
    mstmt.setString(16, results.getString("DANGER_CLASS"));
    mstmt.setString(17, results.getString("ZUSATZGEFAHR1"));
    mstmt.setString(18, results.getString("ZUSATZGEFAHR2"));
    mstmt.setString(19, results.getString("R_PHRASES"));
    mstmt.setString(20, results.getString("S_PHRASES"));
    mstmt.setString(21, results.getString("DANGER_SYMBOL"));
    mstmt.setString(22, results.getString("STORAGE_TEMPERATURE"));
    mstmt.execute();
    
    System.out.println(results.getString("ORDER_NO"));
   }
   
   // clean up
   mstmt.close();
   con.close();
   results.close();
   stmt.close();
   conn.close();
  } catch (Exception e) {
   System.out.println("Oops-> " + e);
  }

 }

}

其實很簡單，和操作數據庫一樣，提供了類似數據中的SQL語句來操作CSV文件中的數據。

#encoding=utf-8
from __future__ import with_statement
import MySQLdb
import urllib
from lister import ListerTR

conn = MySQLdb.connect(host="localhost", user="root", passwd="root", db="coocoo", charset="utf8")
cursor = conn.cursor()
cursor.execute("select id, enname from compound where enname != '' and zhname = '' order by id")
row=cursor.fetchall()
for r in row:
    params = urllib.urlencode({'eng2chi':r[1]})      這里組織參數
    sock = urllib.urlopen("http://202.127.145.134/scdb/translate/translate.asp", params)   發送請求，并把參數傳過去
    html = sock.read()
    sock.close()
    p = ListerTR()   以下為解析返回的數據代碼
    p.feed(html)
    html = p.html
    if u"成功" in html:
        value = p.values[5]
        data = value.strip()
        print r[0], r[1], data    取回翻譯成功的內容更新數據庫里面的值
        cursor.execute("update compound set zhname = %s where id=%s", (data, r[0]))
        conn.commit()
    else:    把翻譯失敗的記錄給文本文件中
        with open('failture.txt', 'a+') as f:
            f.write(str(r[0])+" | "+str(r[1]))
            f.write('\n')
cursor.close()
conn.close()

      mysql-5.0.19.tar.gz

二. 安裝環境:

主服務器:   192.168.0.201

從服務器:   192.168.0.00

三.主服務器配置:

Ø         建立用戶
grant replication slave on *.* to user001@192.168.0.200 identified by ‘111111′

Ø         編輯配置文件/etc/my.cnf
server-id = 1
log-bin=mysql-bin
binlog-do-db=test
binlog-ignore-db=mysql

注:

 # grant replication slave on *.* to ‘用戶名’@'主機’ identified by ‘密碼’;
# binlog-do-db=需要備份的數據庫名，可寫多行
# binlog-ignore-db=不需要備份的數據庫名，可寫多行

       # 可在B Slave上做連接測試: mysql -h 192.168.0.200 -u test -p

四.從服務器配置:

Ø        編輯/etc/my.cnf

server-id=2
server-id=2       記得是兩個???
log-bin=mysql-bin
master-host=192.168.0.201
master-user=user001
master-password=111111
master-port=3306
replicate-do-db=test
replicate-do-db=test1
# replicate-do-db=test  需要備份的數據庫名
# replicate-ignore-db=mysql 忽略的數據庫
# master-connect-retry=60 如果從服務器發現主服務器斷掉，重新連接的時間差(秒)

先手動同步一下主從服務器中要備份的數據庫，再重啟主，從服務器。

五.驗證是否配置正確:

     # mysql>  slave start;

     # mysql>  show slave status\G;

*************************** 1. row ***************************

             Slave_IO_State: Waiting for master to send event

                Master_Host: 192.168.0.201

                Master_User: repluser1

                Master_Port: 3306

              Connect_Retry: 60

            Master_Log_File: mysql-bin.000045

        Read_Master_Log_Pos: 212

             Relay_Log_File: sky-relay-bin.000054

              Relay_Log_Pos: 235

      Relay_Master_Log_File: mysql-bin.000045

           Slave_IO_Running: Yes

          Slave_SQL_Running: Yes

            Replicate_Do_DB: test,test1

        Replicate_Ignore_DB:

         Replicate_Do_Table:

     Replicate_Ignore_Table:

    Replicate_Wild_Do_Table:

Replicate_Wild_Ignore_Table:

                 Last_Errno: 0

                 Last_Error:

               Skip_Counter: 0

        Exec_Master_Log_Pos: 212

            Relay_Log_Space: 235

            Until_Condition: None

             Until_Log_File:

              Until_Log_Pos: 0

         Master_SSL_Allowed: No

         Master_SSL_CA_File:

         Master_SSL_CA_Path:

            Master_SSL_Cert:

          Master_SSL_Cipher:

             Master_SSL_Key:

      Seconds_Behind_Master: 0

1 row in set (0.00 sec)

確如如下行一致:
Waiting for master to send event
Slave_IO_Running: Yes
Slave_SQL_Running: Yes

其他: ++主服務器上的相關命令
show master status
show slave hosts
show logs
show binlog events
purge logs to ‘log_name’
purge logs before ‘date’
reset master(老版本flush master)
set sql_log_bin=

++從服務器上的相關命令
slave start
slave stop
SLAVE STOP IO_THREAD //此線程把master段的日志寫到本地
SLAVE start IO_THREAD
SLAVE STOP SQL_THREAD //此線程把寫到本地的日志應用于數據庫
SLAVE start SQL_THREAD
reset slave
SET GLOBAL SQL_SLAVE_SKIP_COUNTER
load data from master
show slave status(SUPER,REPLICATION CLIENT)
CHANGE MASTER TO MASTER_HOST=, MASTER_PORT=,MASTER_USER=, MASTER_PASSWORD= //動態改變master信息
PURGE MASTER [before ‘date’] 刪除master端已同步過的日志

++產生了mysql-bin.00000x文件可以刪除

附一: mysql無法啟動:

# /usr/local/mysql//bin/mysqld_safe --user=mysql --log-error=err.txt

# more err.txt 根據里面的提示信息進行判斷分析

附二: 解決mysql“Access denied for user 'root'@'localhost'”

mysql -uroot -p
Enter password:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
修改root用戶的密碼：
# mysqladmin -uroot -p password 'newpassword' -

文章出處：http://www.diybl.com/course/6_system/linux/Linuxjs/2008622/127458.html

另一種辦法是在數據庫設計的時候，可能需要大小寫敏感，解決方法是建表時候使用BINARY標示。
CREATE TABLE students(
    name VARCHAR(10) BINARY
);

1. 工資5000以上的職員，工資減少10%
2. 工資在2000到4600之間的職員，工資增加15%

--條件1
UPDATE Personnel
SET salary = salary * 0.9
WHERE salary >= 5000;
--條件2
UPDATE Personnel
SET salary = salary * 1.15
WHERE salary >= 2000 AND salary < 4600;

UPDATE Personnel
SET salary = CASE WHEN salary >= 5000
　            THEN salary * 0.9
WHEN salary >= 2000 AND salary < 4600
THEN salary * 1.15
ELSE salary END;

UPDATE SomeTable
SET p_key = CASE WHEN p_key = 'a'
THEN 'b'
WHEN p_key = 'b'
THEN 'a'
ELSE p_key END
WHERE p_key IN ('a', 'b');

--使用IN的時候
SELECT keyCol,
CASE WHEN keyCol IN ( SELECT keyCol FROM tbl_B )
THEN 'Matched'
ELSE 'Unmatched' END Label
FROM tbl_A;
--使用EXISTS的時候
SELECT keyCol,
CASE WHEN EXISTS ( SELECT * FROM tbl_B
WHERE tbl_A.keyCol = tbl_B.keyCol )
THEN 'Matched'
ELSE 'Unmatched' END Label
FROM tbl_A;

1. 只選修一門課程的人，返回那門課程的ID
2. 選修多門課程的人，返回所選的主課程ID

--條件1：只選擇了一門課程的學生
SELECT std_id, MAX(class_id) AS main_class
FROM Studentclass
GROUP BY std_id
HAVING COUNT(*) = 1;

STD_ID   MAIN_class
------   ----------
300      4
400      5
500      6

--條件2：選擇多門課程的學生
SELECT std_id, class_id AS main_class
FROM Studentclass
WHERE main_class_flg = 'Y' ;

STD_ID  MAIN_class
------  ----------
100     1
200     3

SELECT  std_id,
CASE WHEN COUNT(*) = 1  --只選擇一門課程的學生的情況
THEN MAX(class_id)
ELSE MAX(CASE WHEN main_class_flg = 'Y'
THEN class_id
ELSE NULL END
)
END AS main_class
FROM Studentclass
GROUP BY std_id;

STD_ID   MAIN_class
------   ----------
100      1
200      3
300      4
400      5
500      6

CASE col_1
WHEN 1    　   THEN 'Right'
WHEN NULL  THEN 'Wrong'
END

--簡單Case函數
CASE sex
WHEN '1' THEN '男'
WHEN '2' THEN '女'
ELSE '其他' END
--Case搜索函數
CASE WHEN sex = '1' THEN '男'
WHEN sex = '2' THEN '女'
ELSE '其他' END

--比如說，下面這段SQL，你永遠無法得到“第二類”這個結果
CASE WHEN col_1 IN ( 'a', 'b') THEN '第一類'
WHEN col_1 IN ('a')       THEN '第二類'
ELSE'其他' END

SELECT  SUM(population),
CASE country
WHEN '中國'     THEN '亞洲'
WHEN '印度'     THEN '亞洲'
WHEN '日本'     THEN '亞洲'
WHEN '美國'     THEN '北美洲'
WHEN '加拿大'  THEN '北美洲'
WHEN '墨西哥'  THEN '北美洲'
ELSE '其他' END
FROM    Table_A
GROUP BY CASE country
WHEN '中國'     THEN '亞洲'
WHEN '印度'     THEN '亞洲'
WHEN '日本'     THEN '亞洲'
WHEN '美國'     THEN '北美洲'
WHEN '加拿大'  THEN '北美洲'
WHEN '墨西哥'  THEN '北美洲'
ELSE '其他' END;

SELECT
CASE WHEN salary <= 500 THEN '1'
WHEN salary > 500 AND salary <= 600  THEN '2'
WHEN salary > 600 AND salary <= 800  THEN '3'
WHEN salary > 800 AND salary <= 1000 THEN '4'
ELSE NULL END salary_class,
COUNT(*)
FROM    Table_A
GROUP BY
CASE WHEN salary <= 500 THEN '1'
WHEN salary > 500 AND salary <= 600  THEN '2'
WHEN salary > 600 AND salary <= 800  THEN '3'
WHEN salary > 800 AND salary <= 1000 THEN '4'
ELSE NULL END;

SELECT country,
SUM( CASE WHEN sex = '1' THEN
population ELSE 0 END),  --男性人口
SUM( CASE WHEN sex = '2' THEN
population ELSE 0 END)   --女性人口
FROM  Table_A
GROUP BY country;

CONSTRAINT check_salary CHECK
( CASE WHEN sex = '2'
THEN CASE WHEN salary > 1000
THEN 1 ELSE 0 END
ELSE 1 END = 1 )

CONSTRAINT check_salary CHECK
( sex = '2' AND salary > 1000 )

USE pubs
GO
SELECT
CASE
WHEN price IS NULL THEN 'Unpriced'
WHEN price < 10 THEN 'Bargain'
WHEN price BETWEEN 10 and 20 THEN 'Average'
ELSE 'Gift to impress relatives'
END AS Range,
Title
FROM titles
GROUP BY
CASE
WHEN price IS NULL THEN 'Unpriced'
WHEN price < 10 THEN 'Bargain'
WHEN price BETWEEN 10 and 20 THEN 'Average'
ELSE 'Gift to impress relatives'
END,
Title
ORDER BY
CASE
WHEN price IS NULL THEN 'Unpriced'
WHEN price < 10 THEN 'Bargain'
WHEN price BETWEEN 10 and 20 THEN 'Average'
ELSE 'Gift to impress relatives'
END,
Title
GO

CREATE DATABASE student

2.如何刪除數據庫

DROP DATABASE student

3.如何備份數據庫到磁盤文件

BACKUP DATABASE student to disk=´c:\1234.bak´

4.如何從磁盤文件還原數據庫

RESTORE DATABASE studnet FROM DISK = ´c:\1234.bak´

5.怎樣創建表？

CREATE TABLE Students (
    ID int IDENTITY ( 1, 1), --自增字段,基數1,步長1
    StudentID char (4) NOT NULL ,
    Name char (10) NOT NULL ,
    Age int NULL ,
    Birthday datetime NULL,
    CONSTRAINT PK_Students PRIMARY KEY (StudentID)  --設置主鍵
)

CREATE TABLE Subjects (
    ID int IDENTITY ( 1, 1), --自增字段,基數1,步長1
    ClassID char (4) NOT NULL ,
    ClassName char (10) NOT NULL,
    CONSTRAINT PK_Subjects PRIMARY KEY (ClassID)    --設置主鍵
)

CREATE TABLE Scores (
    ID int IDENTITY ( 1, 1), --自增字段,基數1,步長1
    StudentID char (4) NOT NULL ,
    ClassID char (4) NOT NULL ,
    Score float NOT NULL,
    CONSTRAINT FK_Scores_Students FOREIGN KEY (StudentID) REFERENCES Students(StudentID), --設置外鍵
    CONSTRAINT FK_Scores_Subjects FOREIGN KEY (ClassID) REFERENCES Subjects(ClassID), --設置外鍵
    CONSTRAINT PK_Scores PRIMARY KEY (StudentID,ClassID) --設置主鍵
)

6.怎樣刪除表？

DROP TABLE Students

7.怎樣創建視圖？

CREATE VIEW s_s_s
AS
SELECT Students.Name, Subjects.ClassName, Scores.Score
FROM Scores INNER JOIN
      Students ON Scores.StudentID = Students.StudentID INNER JOIN
      Subjects ON Scores.ClassID = Subjects.ClassID

8.怎樣刪除視圖？

DROP VIEW s_s_s

9.如何創建存儲過程?

CREATE PROCEDURE GetStudent
@age INT,
@birthday DATETIME
AS
SELECT *
FROM students
WHERE Age = @age AND Birthday = @birthday
GO

10.如何刪除存儲過程?

DROP PROCEDURE GetStudent

11.如何創建觸發器?

CREATE TRIGGER reminder
ON Students
FOR INSERT, UPDATE, DELETE
AS
   EXEC master..xp_sendmail ´MaryM´,
      ´Don´´t forget to print a report for the distributors.´
GO

12.如何刪除觸發器?

DROP TRIGGER reminder

13.如何創建索引?

CREATE UNIQUE INDEX IX_Students ON Students (Name)

14.如何刪除索引?

DROP INDEX Students.IX_Students

15.怎樣給表添加字段？

ALTER TABLE Students ADD Address varchar (50) NULL

16.怎樣刪除表中某個字段？

ALTER TABLE Students DROP COLUMN Address

17.如何設置列的標識屬性?

沒找到辦法

18.如何去掉列的標識屬性?

沒有找到好的方法,只能是先添加一列,然后把標識列的值更新到新加入的列,刪除標識列,再用與標識列相同的名字類型添加一列,用前面加入的列更新該列.如果該標識列是其他表的外鍵,還要先刪除外鍵約束,很麻煩.誰有好的辦法,還請告訴我.

19.如何重設標識列的標識種子?

DBCC CHECKIDENT (Student, RESEED, 1)

20.怎樣給表加上主鍵？

ALTER TABLE Scores ADD CONSTRAINT PK_Scores PRIMARY KEY (StudentID,ClassID)

21.怎樣刪除表的主鍵？

ALTER TABLE Scores DROP CONSTRAINT PK_Scores

22.怎樣給表添加一個外鍵？

ALTER TABLE Scores ADD CONSTRAINT FK_Scores_Students FOREIGN KEY (StudentID) REFERENCES Students (StudentID) ON DELETE CASCADE

23.怎樣刪除表的一個外鍵？

ALTER TABLE Scores DROP CONSTRAINT FK_Scores_Students

24.怎樣給字段加上CHECK約束？

ALTER TABLE Students ADD CONSTRAINT CK_Students CHECK (Age > 0)

25.怎樣去掉字段上的CHECK約束？

ALTER TABLE Students DROP CONSTRAINT CK_Students

26.怎樣給字段設置默認值？

ALTER TABLE Students ADD CONSTRAINT DF_Students_Age DEFAULT (18) FOR Age

27.怎樣移去字段的默認值？

ALTER TABLE Students DROP CONSTRAINT DF_Students_Age

28.修改字段的類型及非空約束

ALTER TABLE Students ALTER COLUMN Age char (10) null
ALTER TABLE Students ALTER COLUMN Age int not null

mysqldump -u root -p --default-character-set=gbk testAcegi > c:\testAcegiDump.sql

mysqldump -u root -p --default-character-set=gbk knightsoft > c:\knightsoft.sql

1.   使用
    import MySQLdb
1.1.   連接
    conn =   MySQLdb.Connection(host, user, password, dbname)
1.2.   選擇數據庫，如果上面沒有指定數據庫，則使用此方法指定！
    conn.select_db(’database name’)
1.3.   獲得cursor
    cur =   conn.cursor()
1.4.   cursor位置設定
    cur.scroll(int, mode)
    mode可為相對位置或者絕對位置，分別為relative和absolute。
1.5.   select
    cur.execute(‘select clause’)
    例如
    cur.execute(‘select * from mytable’)

    row = cur.fetchall()
    或者：
    row1 = cur.fetchone()
1.6.   insert
    cur.execute(‘inset clause’)
    例如
    cur.execute("insert into user (Name, Password) values ('maggie','12345')")
    conn.commit()

1.7.   update
    cur.execute(‘update  clause’)
    例如
    cur.execute("update user set Name = 'eric chau' where id = 1")
    conn.commit()

1.8.   delete
    cur.execute(‘delete  clause’)
    例如
    cur.execute("delete from user where id = 1")
    conn.commit()


完整代碼：

from MySQLdb import Connect

def conn():
    #conn = Connect('localhost','root','root')
    #conn.select_db('eric')
    conn = Connect('localhost','root','root','eric')
    cur = conn.cursor()
    cur.execute('select * from user')
    cur.scroll(0)
    row1 = cur.fetchone()
    print 'id:', row1[0]
    print 'name:', row1[1]
    print 'password:', row1[2]
    #cur.execute("insert into user (Name, Password) values ('maggie','12345')")
    #cur.execute("update user set Name = 'eric chau' where id = 1")
    cur.execute("delete from user where id = 11")
    conn.commit()
if __name__=='__main__':
    conn()